samsung galaxy s3 fault

iam now unable to press the power button when the phone is on ,i have to wait for the scrren to time out before i can put it in my pocket otherwise it just gets stuck on the loading screen . any ideas guys

power off
hold down volume up + home + power all at once
wait until the boot screen comes up and it will says recovery in the top left very small, let go at this point
use the volume up and down to scroll and use the home button to select
choose wipe cache
than choose boot system

hopefully that will sort it for ya