Share your experience!
Have you tried force shutdown(power button+vol up until the phone vibrates)?After this,just turn it on normally.
I cannot assure you,but we can wait.Report here if it happens again.It might be related to an overheat,but we will see.
Ok,keep us updated.
Boot your phone in safe mode,see if that will occur again.It might be related to a 3rd party app:
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008
Anytime,I am waiting for your reply.