what gen is that? i know a few gen’s had battery issues… take it to the apple store see if they can take a look at it for free to diagnose it. then find out what the prob is. I suspect a faulty battery and if so then ebay a new battery for like 10 bucks, and swap it and you’ll be good to go.
No reason to drop like 50 dollars on a tech doing it when you barely use it anyways.