There is likely something that Catalina is struggling with. Some latent piece of 32-bit code trying to load in the background, maybe? Same advice I had in another thread: Try Launch Agents and Launch Daemons in your Library folders. We've been having more troubles than ever with those two folders, especially with 10.15. Clearing them out has been super handy at solving more troubles than I can count!
And I do mean "clearing them out!"
Also, have a look at all the remembered devices in the Finder (they used to be in iTunes, and now I think they live in Apple Menu/About This Mac/Storage/Manage and then under iOS Files. Nuke anything old, blah, blah, blah.