Welcome to Android Central! Did this just start? Any recent app installations? Try booting the phone into Safe Mode, according to this article: How do I start my Samsung GT-S7562-BK Galaxy S Duos in Safe Mode? | MobiWhy. Safe Mode temporarily disables all 3rd party apps, so if the problem goes away, it was due to something else you installed. If the problem persists, it's probably an issue with the hardware or firmware.