A few weeks ago I noticed my computer would randomly restart on it's own. I never saw a pattern in when it restarted so I couldn't figure out a cause. One time I was playing a game but plenty of times I would come home from work and find it had restarted when I wasn't touching it. I believe I have all my utilities set to run at night and I work during the day so I don't think that would've caused it. There's no blue screen or error message that I've noticed when it restarts.
Over the weekend however I turned it off for an extended period of time and now when I power it up, it starts to load Windows and restarts before it finishes. It does this whether I try to boot up in safe mode or normally.
I'm not super tech savvy but after doing some research it sounded like it could be a power supply problem so I tried installing a new power supply and that has not changed anything. It still continues to restart.
I haven't made any big software changes that I can think of. As for hardware, I did install some more RAM recently but it was after it had already started restarting on its own as I described in the first paragraph.
I'd appreciate it if someone could lend their thoughts on what to do next.
I'm running Windows XP.