So i recently built an i7 custom rig, windows 7 64 bit, gts-250, 4gb ram. It's been randomly restarting on its own, while i was doing stuff and other times when i wasn't. Just in the past week its been blue screening when i was watching youtube. Ran PC mark vantage and maxed everything out for a good 15 minutes, no issues at all. Any thoughts on what might be causing this?