Your phone is behaving as if it has some malware. Have you run an antivirus scan? Have you done a diagnostic on the phone to make sure all its components are working properly? If resetting the phone works, then reset it, only DON'T restore any backup, because if the backup contains malware, you will only bring it back and repeat the cycle.
After you reset your phone, change your Google, Samsung and email account passwords in case any malware collected those passwords.
