Why it is happening without any reasons
Try to clear the cache of the camera app and force stop the application.
Hi there, kindly follow the below steps:
1. Check your phone for latest software version.
2. Go to Camera settings & try changing focus mode
3. Clear cache & storage of Camera App after backing up & disable/re-enable camera App
4. Try the same under safe mode:
Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode
5. If still you face the issue factory reset your phone after taking a full backup.