Question
When typing the following keys
M / N / J / U
A window will pop up randomly appear which is "Lenovo Custom Program Settings" (Screenshot below)

Answer
Try the step provided below.
- Uninstall Guard ID software. KnowledgeBase article here
- If issue persist, plug in an external keyboard and type on the external keyboard, test and see if the "Lenovo Custom Program Settings " will appear if keys M or N or J or U is entered.
- If there is no issue when using external keyboard, do contact service to get the laptop checked.