The phone lives and dies on its own

@addinkaran95313 this could be caused by an aging battery. Replace the battery and then re-evaluate. since iFixit does not yet have a specific guide for that, use something like this video Replacement batteries are readily available at many online stores. Since there are a lot of counterfeit batteries around, you do want to purchase from a seller that has a good reputation.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!