With the PC booted up what would cause a screen to intermittently black out and come on again almost immediately? This has started to occur over the past week or so. - this is when not being accessed and without any movement of PC.
Yes, but as stated senior problems. I have had another PC problem for the past two weeks that has taken that long to eliminate the culprit and today I finally found the culprit after a process of very, very slow elimination. The main thing was that is was an intermittent one, much the same as now with the monitor.
I don't know whether you have tried another monitor yet or not but the reason I replied originally was that I had a similar though not exactly the same thing with one of my PC's which my daughter uses, tried new cables no result it still did it but totally at random. Tried another monitor and that was fine, put back the original monitor and it started again so I have narrowed it down to the monitor itself. Tried it on another PC and it seemed OK. I have now put it back on my daughters PC and it will still do it. In the end I concluded that it was a dry joint from the input port to the monitor PCB. So in my case a new monitor or wiggle the input cable around and it may be OK for 5mins or a fortnight. Your case may be a completely different scenario but that is why my first thought is to try another monitor.
I will get the other monitor down for the weekend, but after having another very intermittent problem (now hopefully solved -I DID NOT SAY THAT)for the past fortnight I feel I need a rest for a couple of days.