I was asked to look at a misbehaving laptop recently (a hazard of this profession). “It seems to works fine, then shuts itself down without any warning,” I was told.
Yesterday the same happened to me. I was typing away when bam! the PC turned itself off.
The reason in both cases was the same. Dust. When I took the back off the PC I saw that the fins on the heat sink were completely clogged and it was no longer cooling the CPU effectively. When the CPU overheats its thermal protection kicks in and turns it off.
The laptop was a variation of the same problem. Some of the vents in the case were filled with dust and dirt, impeding the flow of air. Apparently this is a common problem with some Acer models.
Part of the problem lies with Intel for making CPUs that run so hot. Cooling is critical.
Fortunately the fix is easy, though you normally need to take the back off. I used one of those aerosols that squirts out compressed air. Clean out the dust and it all runs sweetly again. If only all system failures had such simple solutions.