To save as much power as possible, I always switch off my M58p at the wall when not in use. When I want to use it, I switch power on at the wall socket and the PC receives power and for a few seconds lights come on and go out and the fan spins momentarily. Once it has done this and powered itself off, I can then press the power on button the front of the M58p and it boots up to Linux just fine.
What is going on when mains power is turned on? Why does it power on then off a few seconds later? Can I disable this somehow?