I am also having issues with my 2018 radio somewhat similar to yours. About a year after I purchased the truck my radio would randomly turn off, when I had my phone connected via Bluetooth, and go through the restart process like when your turn the truck on. It then reconnects to the phone and 5 or so minutes later does the same thing all over forever and ever. I have tried disconnecting the phone and repairing them all over from scratch and the problem remains. Service tech at the dealership said it’s because my phone is too new (iPhoneX running iOS 13.3.1). I find it hard to believe that everyone with a Toyota can’t use their Bluetooth, but maybe I’m wrong. Were you able to resolve your issue?