I have this problem - with a BRAND new phone (S4 mini, i9195, 4.2.2, I9195XXUAMF5, 3.4.0-870901, JDQ39.I9195XXUAMF5).
2 days after buying it, it started rebooting, about once every two days. After a week, the store has checked my battery and said it was bad (was outputting too high voltage)...