Verified answer

Go to Safe mode and go to startup programs. Check to see if the system reboot thing is on the start up programs.

I assume you are using Windows, but depending on the OS, there are countless reasons and responses to your problem.

First thing I would suggest is restarting your computer and entering into safemode.

there are several ways of getting into this mode, one by turning the computer off abruptly and then restarting it. You will then be asked if you want to start up in safe-mode.

From there I would do a diskfrag, virus scan and adware check.