My tablet keeps turning off by itself

Hello everyone, so here’s my problem: my tablet also shuts down by itself while I’m busy doing things on it, even though there’s plenty of battery left. When I plug it in to charge, I hear a small noise and sometimes it doesn’t charge fast enough, so I don’t really know what to do. I reinstalled it and I'm waiting to see, but it starts doing this when I don’t have a warranty anymore. I've had it for over 2 years. Thanks to those who will reply.

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