Safe Mode puts your phone in a diagnostic state (returned to default settings) so you can determine if a third-party app is causing your device to freeze, reset or run slow.
With the device powered off, press and hold the Power button (located on the right edge) until the Samsung logo displays then release.
Once the SAMSUNG logo displays, quickly press and hold the Volume Down button (located on the left edge) until Safe mode displays in the lower-left corner of the screen then release.
With Safe Mode enabled, test device and app functionality. If the previous issue fails to occur, the cause has been isolated to a third-party app and all recently installed or updated apps should be uninstalled.
Power cycle the device to disable Safe Mode then reinstall and test each app one at a time to identify which app is causing the problem.