120 fps games now running at 10

[alan4friddle]

I can often get games like fortnite at over 100 FPS but now I can barely get it running at 20 FPS. This started out of nowhere and I can't find the issue. All of my games run at low FPS such as Planet Coaster and Hitman.
Also, my PC will randomly shut off and then reboot. But when it reboots my TV displays NO SIGNAL. What may be causing the issue?

 

[t99]

What specs?

 

[Peter Martin]

check installed updates. see if your graphics driver got replaced recently

 

[alan4friddle]

What specs?

I don't exactly remember but I know I have 16 gigs of RAM and a GTX 950