You can check whether the application is by booting to Safe Mode may be the culprit. Turn off the phone, press and hold the power button. When the screen lights up, let go power and hold the volume down button. It should be said in Safe Mode in the lower left corner. You can get rid of the restart in Safe Mode. If there is no problem in Safe Mode, then what you have installed may be causing the problem. You can try to uninstall things and test one by one, or choose to restore the factory settings, and installed options. If you doing a factory reset, it might be wise not to restore a backup, just set the S6 instead of fresh because the problem you may be re-introduced.