Hi dear, follow these steps to troubleshoot the issue. 1. Check if your phone is getting restarted when the charger is connected. If it doesn't then it's battery issue. Still restarts follow the next step. 2. Check your phones power button. Try locking and unlocking your phone continuously. If the button have some problem that's causing the issue. If the button is ok then, 3. Try installing the software through Smart Switch or Odin. Smart Switch is less complicated but Odin is faster. If you don't know how to install software, take your phone to a nearest service center.
