Then it might be a combination of factors.
Like too many bots while at the same time one of your DIMM's went bust.
Also whenever it happens again, Ctrl+alt+del to check if one of those damm svchost processes goes thru the roof.
Got a older GFX card lying around ? Try changing it, or borrow one from a mate.
Plenty of possible causes still open
(Finished Great alligator btw. Tnx.
You can unshare it now. I'll be the lighthouse.)