Oh don't worry this is a frequent occurance on my iPhone it is usually caused by apps not shutting properly that use a scrollbar at the bottom of the screen in some way. Atleast this is the cause on the iphone.
Atleast yours doesnt enter the debug/diagnostics mode and select automatic by it self every few hours.... I hate when it does that cause it locks up on the accessories test.. Updated software everything, it just does it, for no reason