Question Monitor half green flash

[Dreadbeard]

I'm looking for some advice, when I start or restart my pc, just before booting the bottom half of my screen flashes green, then it boots like normal - it seems like everything works as intended but I don't have any clue why it does it? Any advice as what it could be?
It also takes quite a while for my pc to load from post to desktop
Video of the flash

 

[helpstar]

check the windows event log for errors at the time of the booting
check with dism commands for errors
fast boot and UEFI boot is enabled?

 

[Dreadbeard]

check the windows event log for errors at the time of the booting
check with dism commands for errors
fast boot and UEFI boot is enabled?

How would i go about doing any of the above?