Why is my battery overheating despite very low usage?

[AC Question]

I have a galaxy Samsung tab 4. The battery has already had to be sent in for repair and replaced. In the last few weeks, there was an issue with the SD card which I have since removed altogether. The device regularly states that it is overheating and a number of apps have been closed - I never have the number it states running so not sure what that's about. Battery then shows it's drained to next to nothing. When I restart it, battery shows high 80s. Any ideas on how to fix it? Other than sending it back in and losing all my data??