Vivo v15 sweth off problem

@bimaldas it sounds like you are saying that your phone switches off. In that case I suggest that you start with a new battery. IF that does not resolve it, you will at least have a "known-well" starting point. Since iFixit does not yet have a guide for this, use something like this video to work on your phone.

We need more information on this phone and its symptoms to really be of help to you. The more information you provide, the greater the chance of getting a helpful answer.