Is this a PSU problem?
I have a 1000GT, which is only about a year or 2 old, and every now and then, my computer just shuts off. I'd say it happens 1-2 times a week. There are no other issues; everything is fine; it doesn't matter if I'm gaming or just watching a YouTube video. It's just off turns off, and restarts.
No overclock on ram or CPU or GPU.. The computer has been stable since the last time I was having weird issues where the 5900x CPU just randomly died and couldn't hold stock clocks.