My PC turns itself off, can anyone help?

[mermaid]

Hi, My Pc turns itself off. If I leave it on for varying amounts of time, it will turn off. It is sometimes difficult to turn it back on. I actually have to unplug it then re plug it in at the back and then it will start.
By the way... I have no idea what I'm doing so please tell me as simply as possible.
Thanks

 

[ryanstrassburg]

What OS are you running?

Sounds like your system memory has taken a crap (or rather a portion within a chip), typically when I had a bad memory chip this is what would happen when the bad memory segment was accessed. When booting (I assume you are using Windows) press/hold F8 just after POST and run a memory diagnostic (you have the option to load Windows or run a memory diagnostic), this may detect a problem but requires no fiddling. If not and the problem persists then I would suggest swapping out the memory chips on the motherboard, or use one at a time if possible to see if one is bad.