Your computer monitor briefly goes black for a second and then returns to normal. The power LED stays on. Everything seems fine — until it happens again 10 minutes later. Or 2 minutes. Or every 30 ...
I have a G-Sync compatible monitor, and if G-Sync is enabled my monitor will go black for about a second if I open a store page in STEAM and scroll the video out of view. It will then go black again ...