my screen goes black when i tab in and out of games plus when i full screen yt vid

[glacial sparrow]

my screen goes black when i tab in and out of games for a few seconds on top of that when im browsing or watching yt when i full screen my screen goes black and if i move my mouse it goes back to normal if i leave it be it goes black again gpu rtx 2060 on pc

[torn kettle]

same i also have rtx 2060 ..my screen goes black and fan speed goes at 100% and then i have to restart my pc using the power button on my cabinet.