Bluetooth is not working (maybe reconnecting ...)
Reset PRAM/NVRAM after updating to Catalina so that any old data should be removed from the cache.


Shut down your Mac.
Turn it on and immediately press and hold these four keys together: Option, Command, P, and R.
You can release the keys after about 20 seconds, during which your Mac might appear to restart.


It will resolved your issue. This solution worked in a couple of Macbooks of my colleagues after upgrading.