Why is the bluetooth connection spotty?

I have an old Macbook Pro I got from a friend that overall works great, except for the Bluetooth.

The main thing I've noticed is that when I connect my Airpods to it, the connection seems to drop out at random times. It usually comes back after about 30 seconds - a minute, but I haven't noticed anything that could be causing that. I'm 99% sure it's not the Airpods because they connect fine to my phone and every other device I've paired them with.

Also, a few days ago I tried to connect a Bluetooth mouse - one of the older ones that has a USB thing that needs to be plugged in to connect - and the Mac seemed to thing I was attaching a keyboard instead of a mouse and tried to get me to sync the keyboard to it by tapping a few keys. Which, of course, didn't work because it wasn't a keyboard.

Has anyone seen this problem before/knows how to fix it?