I get the black screen of death after letting my pc sit

So for the past 2 days Ive been going AFK for a few hours and when I get back my PC screen turns on but its just completely black screen of death. I dont know whats wrong and I have to restart it for it for anything to work again. Also when I start up my PC it loads incredibly slow and I cannot see anything besides my mouse for a good 10 minutes. I can control alt delete and click things but nothing will load. But then once it does load it functions as normally and I have NO idea whats wrong.

I don't know whether it is a malware issue. Please clean your pc by creating new topic here. Details --> here

I had it too on my PC and it was after a windows update, so you probably want to check what windows update did recently