Galaxy S3 GT-I9300 version 4.1.2. stuck and freeze I have Galaxy S3 GT-I9300 version 4.1.2. Lately it freezes very often and only a restart helps solving that.

I ran Factory data reset, but it does not help.

I don't know how to solve the problem. I bought it less than 1 year ago via E-Bay so I don't know who can help me.
As a recommendation, try installing a custom ROM like CyanogenMod 10.1. You won't lose your apps, and this happened to me on my BN Nook Tablet (rooted) and installing CM fixed it.