HDMI cable artifacts

Anyone knows what this could be?


I’m not sure if this is cable, graphics card or screen. The black color is image I made to make artifacts more visible. When it goes totally black it’s because the screen turns off. I think it’s related to heat. When screen is off (either PC is on or not doesn’t make difference) for some time it cools down. When I turn on the screen, for about five minutes it won’t do that. Then it starts doing that for about five minutes and when heated enough it stops. The screen’s adaptor is very hot. I almost burn when I touch it.