I have the same issue.
I have just installed unreal engine 4 and upon launching it I noticed that every time I move my mouse it causes my screen to go black for about a second or two. At first I thought it was my resolution so I turned it down to 1920x1080 (was at 3840x2160) but the problem persists.
I have no idea what could be causing this issue however I am currently updating my graphics drivers to see if it resolves the issue.
My GPU is a 1070 with driver version 411.70 (I can’t roll back because I need the latest drivers for Forza horizon 4).
Edit: after updating to the latest drivers, restarting and changing my resolution to 1080p the screen doesn’t flicker as often now, however it still flickers whenever I open and close pop up menus.