I have a T-Mobile Samsung S2 and this week it started randomly rebooting itself. I cleared cache, did a fresh install and even tried stock ROM but no hope. I noticed that the phone reboots when I open mobile data. The phone is fine until I enter sim pin and the moment it establishes an internet connection through mobile data it reboots. Although 3g is fine while charging. Thought it might be a battery issue, but there is no problem when I disable 3g and while I'm on recovery. Running Sultan CM 11.