Monitor weirdness
I have three monitors on my Office PC. Shortly after I moved to my present location I found that one of them randomly goes black and mostly comes straight back on. Occasionally though it stays black and it is necessary to switch it off and leave it perhaps 10 minutes before I can get it back to life.
Eventually I realised that this flicker only occurs when someone uses the shredder. It doesn't happen every time the shredder is used and it's better than it was now I have a surge protector extension lead on it, but it is still an annoyance.