Can you try your phone in Safe Mode? Using Safe Mode on a Samsung phone or tablet allows you to force the device to run the essential operating system, and disable most 3rd party applications. It's designed as a diagnostic tool to help solve issues with connectivity, battery life, apps, and more. To do this press and hold the Power button until you see Power Off, Restart and Emergency. Press and hold the Power Off icon until it shows a Shield, tap the Shield and the device will restart in Safe Mode. Once done, try to take a picture using the timer. Are you able to see the countdown whilst the phone is performing on this mode?