I've found a way where I can more or less constantly reproduce the issue now.
If I'm in another app for several minutes, and say I have Outlook open but it is behind the app I'm currently in, if I move my mouse down to the task bar and hover over the Outlook icon so I get the thumbnail preview, then click on the preview itself like
I want to go to that app - that's when it happens.
All video will pause for a second or two, the screen will go black, then everything will come back and Outlook will be maximized full screen.
It's definitely something to do with the graphics driver.