Why does my galaxy tab2 10.1 keep restarting itself?

[AC Question]

Hi my tab 2 10.1 keeps restarting itself every time I try to change any of the settings.
I have tried to turn it off rather than restart it but it before it's shuts down it restarts anyway.
I tried to uninstall an application, the uninstall completed but then it restarted itself again and the uninstalled application was back on there, the application I was trying to take off was avast battery optimiser.
Any help would be appreciated - thanks

 

[n7mafia]

Are you sporting a custom rom or original samsung?