Samsung has issue with there battery connectors all you need to do when it acts up is disconnect the battery and wait a few minutes then reconnect it . Here's a video explaining how to do it . I would not use anything but plastic to open the case a plastic knife or guitar picks or a spurge if you have one available to you. Metal knives can do damage to soft plastic circuit boards and cases
https://www.youtube.com/watch?v=lIi__P86hyA
Hope this helps