Four weeks ago I bought a c940. Thirteen days later this happened to me exactly. It could not be shut down or turned on. Pressing the power button caused the key backlights to flash at regular intervals but it didn't seem to turn off (screen black but still hot). It was disconnected from power and left overnight. In the morning I put it back on the charger, booted up, backed up my work, and exchanged the computer for a new one. Today the new computer -14 days into use -has done same thing. It is overheated after being in sleep mode. I managed to turn it off and it has cooled and rebooted. 

Same issue, my brand new laptop got extremely hot after the second time I used it, and had closed the lid. I went to do something else (it wasn't plugged in btw), and a few hours later I came back and tried to pick it up and it was so hot it burnt my hand and I couldn't pick it up. It is brand new, this is the second time I was using it, the first time being just general setup and updates, I had only installed one program (discord), and after a video call on discord is when I closed the laptop and this issue occurred. Now I’m giving the benefit of the doubt that it could’ve been discord, it could be a Windows 10 issue, etc, but I was so scared this would permanently damage my laptop that I turned off a ton of settings (for example I disabled discord to open on startup, I changed the setting so that the laptop goes to hibernate instead of sleep when I close the lid, etc). This seems to have worked, but I'm concerned that this is an issue with my laptop or that it may have been permanently damaged. Like I said I've only had it for a few days. I spent a long time picking out this specific laptop, was torn between the thinkpad x1 extreme touchscreen (which I was able to find at a comparable price to the sale price of the c940 on walmart.com), and finally decided on the c940 because of the fact that it is a yoga, whereas the x1 extreme is available as a touchscreen but I think it may be hard to draw on since it does to the 'yoga' thing. The x1 yoga just has nowhere near comparable specs to the c940. I don't see any updates to this thread, has anyone figured out what the issue is? I read a ton of reviews before buying this laptop and the common problem that I saw was that the fans are always on and that it gets hot, but this is not normal laptop heat temperatures, this was literally like touching a hot stove. Is there really something inherently wrong with this laptop? Should I try and exchange it? Or is this just a windows issue, that I'll constantly have to be tweaking setting and stuff like this. (btw, I had a thinkpad t60 over a decade ago, then switched to mac about 5 years ago, and now bought this as a second laptop even though my MacBook pro from 2014 still works great there are some programs that just work better on pc that I need for work). 

No solution to this issue has been identified to the best of my knowledge.  Disabling sleep mode completely and replacing it with hibernate mode has been an effective work-around for me, but this is not a real solution.  In my view, there is something wrong with the cooling logic in this laptop.  I have several other laptops that I use in addition to my Yoga C940 (all different brands than Lenovo - Dell, Toshiba). None of them exhibit this overheating problem in sleep mode.  Consequently, I do not believe this is a Windows 10 issue.  I think it is a Lenovo issue.

Lenovo needs to fix this.  Overheating is a real safety issue.

Yeah this definitely seems to be an issue with this model of laptop, there another thread with two others describing the exact same issue...

what I first described happened a week ago, now every time I use this laptop (which so far still hasn't been a ton, I bought it as a secondary laptop so I'm gradually transitioning to working on it), whenever I close to lid (which I have set to hibernate when I do so), the next day when I open the lid back up it doesn't turn on the screen and I have to press the power button to turn it back on, and when I do so it shows the Lenovo logo then brings me to the login screen, I'm assuming this means it shutting down? Is this normal for hibernate?

Yes.  It's my understanding that in hibernate mode, the laptop completely shuts down.  Before it shuts down, though, it writes a hibernation file to disk that is essentially the state of the computer at the time you go into hibernate.  Then, when you power up again, the contents of the hibernation file are loaded into RAM.  So, your computer returns to the state it was in before you went into hibernate.   If you had applications open before hibernate, they are now open after hibernate.  Because the computer shuts down in hibernate, it will not overheat.

In sleep mode, the computer never shuts down.  The computer goes into a low power state, but the RAM remains energized.  Thus, heat is being generated.  If cooling is not maintained, the computer will eventually overheat in sleep mode.  This is what seems to be happening with my Yoga C940.

For me, the functional difference between hibernate and sleep is small (just a few extra seconds of boot time for hibernate).  So, I'm fine with using hibernate mode instead of sleep mode from a functional standpoint.  Having said that, it is not acceptable to me that the computer will overheat in sleep mode.  This indicates some flaw in the cooling system or logic.  This really needs to be fixed.  It's a safety issue.

I recommend completely disabling sleep mode and switching to hibernate until Lenovo fixes this issue (if that ever happens).  I set up my laptop to go into hibernate when the lid is closed, but forgot about the laptop going into sleep mode after an extended idle time (without closing the lid).  I was away from the laptop once for a couple of hours and came back to find it extremely hot.

Since I have completely disabled sleep mode, I have had no overheating issues.  I'm hoping Lenovo is reading these posts and will do something about this.

Using hibernate mode is not a solution; it is a work-around.  Lenovo needs to diagnose this problem and fix it.

Fat chance of that. They release new laptops every week but never fix their buggy ones.

The C940 has been out for ages now and is still a buggy unreliable mess.

Thanks for clarifying, yeah I've switched my settings to hibernate, its really unfortunately I did a ton of research before getting this laptop and had seen a lot people saying stuff about the laptop heating up and the fan being on all the time (which actually I haven't had those problems, it barely gets warm when I'm using it unless I'm on a zoom or something, and even then pretty normal warmth, its actually cool to the touch almost all the time I'm using it, its ONLY when its in sleep mode that it gets hot, which makes it all the more annoying, otherwise the fan kicks in at the proper time and works well), but that seemed like more of a noise issue, idk maybe we just got lemons, its too late for me to return it, unfortunately I didn't start to use it right away because I got it as a secondary laptop.

Same for me, using hibernate is not too much of an issue, its a minor inconvenience but its just like you're saying it really sucks that I have such a major safety issue on a brand new laptop. I got a Lenovo because the last windows laptop I used a decade ago was a T60, and that thing still works great (great for it being a decade old), at this point I feel like I would've just been better off upgrading that old beast. 

If I can complain in a more general annoyance sense for a second: I actually have a similar issue with my phone (an iphone 11 pro, so I know this isn't relevant to this thread at all, but idk I'm just venting at this point as it seems hopeless to get a real solution), but that's another premium product that I purchased based on previous brand experience (always good, judge me if you want but until this phone apple products always worked really well for me), and it also heats up, but there's no hibernate setting I can change on my phone, and its a similar problem in the sense that on the apple forums there's no real fix other than the generic stuff people say for every problem. In this case it heats up just browsing the internet, and its just infuriating that a brand new premium device has a major flaw, especially in both cases its a heat related one, from two completely different brands. Was there just a bad batch of batteries this year? I know I'm grasping at straws lol