All you are doing is switching the monitor off and on? This in no way affects Windows, so yes, its probably a monitor issue. The only other possibility I can think of is that Windows is in fact taking a long time to load, and that if you dont turn the monitor on and off, it wont make any difference and the desktop will still eventually appear and stay there.Try not turning the monitor off and see if the desktop does actually eventually load properly, and timing this. If it does, then try again. timing how long it takes you to get the desktop up properly switching monitor on and off.
Mitz from Tips4pc