Why is this doing this?
Did you try removing your battery for a few minutes? Then make sure it and the back is installed firmly? (Not sure if the s3 has a removable battery.)
I will give it a try. Its removable, I did take it out but placed it back in. Before it went into this cycle it would get really hot.
How long have you had the phone?
While it's on I would back up any important documents files to your cloud. Just in case.
Have you ever done a factory reset on the device?
20 Months - the problem I can't do anything it just turns on and off on a rotating cycle. as soon as it loads it shuts off then comes back on and reloads.
Shut it down completely and then hold the volume key and power key together until a screen appears. You can from there start it in safe mode and see if that helps.
