Well, on a 2019 G05 and a N20U (SM-986U1), I've had the exact same described experience with the random drops, involved reconnect process, etc.
Was happening on 07/2020 & is still happening for me on 11/2020, though I lean towards this being an Android Auto bug more than iDrive.
N20U is currently running Android 11 w/ OneUI 3.0.
G05 is currently running 11/2020.45.
Edit: just went on a nice 30 minute morning drive and had 2 AA restarts during the trip. First was when I tried ending a phone call - the entire iDrive console in the center went blank and then rebooted, logo and all, and when it restarted, it recognized my N20U was connected, but wouldn't start in AA. N20U kept showing the "Rate your feedback with AA"/System Driving App is Running messages and showing signs that it recognized the AA enabled vehicle, but just couldn't connect. Restarted the vehicle, kept going for another 15 mins, and then it cut out on me when I (admittedly for the purpose of tripping it up) tried changing the song on Spotify via my phone app instead of the iDrive console. Welp. Here we go againnnnn. This guy is headed back in on Monday for the 13th time in 12 months now due to a continuing dash cluster failure issue, so I'll mention this then and see if there's anything my case manager or engineer can add to this discussion!