I had this problem and returned my first phone. Restored my backup to the new phone and had it again a week later. Did a full reset on the phone (factory specs) and manually re-setup my phone (only used the backup for contacts and images I believe). Haven't had it happen since - so it was something I did somewhere along the line that messed this up. I couldn't tell you what it was, but try resetting your phone back to factory settings and go from there, don't restore settings or apps, only contacts and images.