This isn't a common problem (that I am aware of anyway). So it may be the result of a failing part within the monitor itself. Do you have another monitor or a TV that you can switch it out for. Then observe the new monitor for same problem. If it repeats then the problem is within the PC (most likely the graphics card). If the problem doesn't reappear, then the problem is isolated to the old monitor.
Likewise the integrated graphics can be used to isolate the graphics card (if it gets that far). Troubleshoot the problem backwards from the monitor.