Why is my Windows 10 system behaving oddly?

[sophallee]

My Windows 10 machine is playing up and do really weird things:
* Start menu intermittently pops up
* Application enters and exits full screen
* Mouse cursor intermittently shows up in full screen mode

Thank you in advance.

 

[realwarder]

I would check for a virus/malware.

Run this on another PC to create a boot disk and follow instructions: https://support.microsoft.com/en-us/help/17466/windows-defender-offline-help-protect-my-pc