I've had this problem, where Touchwiz keeps locking up and auto-resetting in a loop. It happened with my current phone last night, which is a replacement S3 for the one I bought in July. That one had the same problem, and I had reset it about 4 or 5 times prior to getting a replacement.
It's getting old fast. Actually, it's already old. Does anyone have any suggestions or hints as to what's going on with this? The phone is awesome, up until the point it isn't anymore. Then it sucks hard. I'm getting tired of rebuilding my phone every few weeks.