Airpods randomly disconnecting from my phone

I inherited these AirPods from my mom, and she couldn't remember any damage that it received, so I don't know of any possible causes.

Problem: I will be listening to music with my airpods' battery in the 90s. And suddenly one of them (and some times both) will stop working. This happened in intervals varying from 3 minutes to 10. When they stopped working, I would put them into the case for a minute, and this would seem to fix it.

At the moment, I am trying to completely drain the battery to try to recalibrate it to see if that might be the issue.

Edit: P.S.: Sometimes my airpods will run for quite a long time as they should.