Check your computer's power source and cables, as a loose connection might cause restarts. Make sure your computer is not overheating, as this can force it to restart. Updating Windows and ...

My first thoughts would be to check your power supply and check you temps. Could be a power supply failing or it could be your fans are clogged with dust and you are reaching higher temps.

Speed up your PC with 3 simple Windows tweaks—no restart needed.