So three times in a row now since yesterday evening, my PC will seem to be running fine and then all of a sudden the screen will shut off and all the fans on my GPU will go 100%. I checked MSI Afterburner and the GPU temps were only about 54 and it's cold in my house. The rest of the PC is fine cause I can hear Windows in the background. Any suggestions on what else to try? 
 
Drivers have not recently been update, so I don't think that's a problem. Windows Update is set so that I have to run it if I want any updates. 

Thanks. The primary concern for me is the fans suddenly spinning up. If it were just the black screen I'd lean more towards your suggestions, but since the fans spin up at the same time, that makes me think a hardware issue. 
 
I only have one monitor, so can't test that. I can check the voltage on my GPU power, but would think that if that was an issue, it wouldn't boot up and run fine for a few minutes before this happens. Could be wrong though.

That's what I was thinking. I don't have any other GPU to test with, and my CPU doesn't have integrated graphics.