The software or work you are doing on your PC is not capable to handle your card. It is my personal opinion. Might possible your card is old and not enough to work with the latest updates on your software or games whatever you are using. It is also possible that at some point may crash your display because all other time it is working. It should not work any time if there is a card or PC issue.
One thing you cantry simply format your PC and try to check the problem still presists.