My pc might have a problem

The thing is, I just don't know what that problem is.
I was happily playing Skyrim. Paused it because it was launchtime, then when I go back, it's shut down. I say, okay, that happened before. (temporary power outage)
But when I push the power button, nothing happened. I almost freaked out. I thought my power supply died. But to know if it wasn't that, I tried to turn it on a few minutes after, and it worked.
I can buy a new power supply if that's the problem. I just hope it's not more.
Please help me.
Thx.

hmmm... I would monitor the temp and make sure nothing is over heating. That is 1 possible cause for your problem.

Try to re-connect your HDD or RAM, that's what happened to me, even when I press that start button of my CPU it beeps for a long time then does nothing. Probably from over heating or that its simply dying.

I had a situation like that once. Turned out to be the motherboard. Check and see if it happens again.

just check the sleepmode settings

turn it to 2 hours-never

this would be the case if you where away for longer than 30 min

"then when I go back, it's shut down."

Try Cleaning your Unit. But,
It happens to me before, its indeed the power supply, buy a new one bro.