We try another monitor on this PC and this monitor on another PC.
That usually determines what to do next.
I'm dealing with an HP 2011x monitor and Inspiron 3847 box running windows 10.
The video signal between computer and monitor seems to be cycling on and off. For a few seconds I can see a computer screen (website, spreadsheet, whatever), and then that turns off to be replaced for a few seconds by a "check video cable" message, then a few seconds later the screen becomes active again, and then the "check video cable" comes back again etc, etc, etc.
I have rebooted the computer, rebooted the monitor, and verified that the video cables are properly attached.
I'm guessing that the video card is about to go belly up. Anyone have any other ideas?
Thanks in advance for any help.