Computer not shutting down

so this really weird thing started happening to my computer when I go to the start menu and then shut it down from there, it sometimes doesnt shut down and the screen is just a black color, like the monitor is still receaving a signal from the tower or something. it sometimes shuts down 20 minuts after this, but just recently I had to unplug it to shut it down. do you guys know why it started doing this?

make sure your page file isn't being erased on shutdown