Sudden switch off again and again

@aryankumar57518 "Bloated back" is a pretty good indication that your battery has failed. It is expanding and will need to be replaced. Do it now before it gets' to the point where it "vents with flame" (explodes :-) I would also suggest that for now you stop charging your phone since that can potentially make things a lot worse.

Since iFixit does not yet hve a specific guide for this, use something like this video to replace the battery. Replacement batteries are readily available at many online stores.

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 the same issues with their device. 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!