This problem has happened before. After a black out or something the computer would turn itself on and off continuously until I unplugged it. Just last week it started happening regularly. The computer would start up, but the lights on the motherboard would go off after a few seconds and everything else worked fine. I thought maybe I just needed to clean the dust out of the PC, so I did. I took out the CPU heat sink and cleaned it. I tried to put it back in, but I noticed that the plastic part on the bottom of the heat sink was broken and could not be properly placed back in. I also noticed that the thermal paste was all gone.
I know I'll probably need to buy a new heat sink so feel free to recommend some. Any ideas what the problem before that was?
this problem seems very vague. it can be many things
try clearing your cmos first off and try booting again
if you have extra parts laying around or an extra similar computer that your willing to temperately sacrifice so you can troubleshoot by swapping parts and ruling out possible problems.
If the CPU fan is not set properly and there is no thermal paste, it is very possible the CPU is overheating.
First things first, get a new CPU heatsink and Fan, if problem persists after that, replace the PSU, still having issues get a new CPU. If none of that works.. Get a new MOBO, and a friggin UPS.
my friend had that issue, his core i7 computer would turn off 5 minutes after being on unless it was on its side. and it ran really slow when it was on. it ended up that his stock intel heatsink had un pinned because they suck.
Try putting on some thermal paste, and holding the cooler on the CPU firmly so it works well, if this solves it you can be pretty sure its an overheating problem, just get a new cooler