Samsung phones, both the Galaxy S10 and Galaxy S20, Google Pixel, and Xiaomi devices are all said to be impacted by this problem, with no workaround known to exist.
“I’ve been having the same issue. I use Android Auto whenever I’m in my car but recently I’ve been so frustrated I don't even bother anymore. My phone disconnects at the slightest touch, turn of the car, or for no reason at all. Half the time it doesn't connect at all. I’ve tried different cables, turning my phone on and off, turning my car off and on, and nothing helps. When it does connect it'll work for a while then randomly disconnects and it won't reconnect at all. I have a Samsung Galaxy S20 Ultra and a 2018 Subaru Impreza,” one user explains on Google’s forums.
At this point, Google is yet to acknowledge the problem, but again, random disconnects on Android Auto have been around for a long time, so it’s hard to say if the one to blame is indeed a recent app update or something else has triggered this behavior for more users recently.
If you’re certain the whole problem is caused by an Android Auto update, one thing worth trying could be a possible downgrade to an older version of the app. On the other hand, replacing cables and trying new ones don’t seem to bring things back to normal, so the generic workarounds are pretty much useless this time.