I've recently been tinkering with my PC, I overclocked my GPU and ran superposition for ~15 minutes, the max temp was 72C on the GPU and 60C on the CPU.
After 15 minutes one monitor (Display Port) went black and said "No Signal", the other monitor (HDMI) was fine.
I restarted the PC, got rid of the overclock (both CPU and GPU) and it was working fine for a few hours at which point the same thing happened, display port monitor black, hdmi is still fine (note this happened while browing reddit and watching a youtube video).
Specs:
Ryzen 5 2600 (was overclocked to 4Ghz @1.375V
MSI GTX 1060 6GB OCV1 - Overclocked using this video: https://www.youtube.com/watch?v=-9wsDqsObcg
Corsair Vengeance LPX 16GB (2x8) @3200Mhz, upped it from 3000 yesterday, PC has been fine and stable.
Asus Prime B450M-K
Corsair CX600M
Also note that the PC is running fine currently, although the main monitor is still not working, typing this on the HDMI one.
Edit: Set the ram back to 3000Mhz, monitor still wasn't working, turned it off and let it sit for a minute, updated GPU drivers and it's working fine now.
Could still use an answer for this though because I feel like it will happen again.