@beardalaxy
It's not important, I just have 2 PCs connected to the primary monitor of one of them, so when I turn the other one first, it takes it over, and I have to switch a few times to make things clear.
But, it's not important. At least I can work with both PCs as dual monitor when needed.
@LukeAlmighty so you gave two PCs plugged into one monitor. There should be a setting on your monitor to disable automatic input switching. I don't think that's a windows problem, if I understand correctly. It's just that windows will send a signal to a monitor that is sleeping or turned to a different input that it's time to wake up or switch. Consoles do this too. I think on ps4/ps5 you can turn that functionality off, but you can also do it on most monitors/TVs.