I first reported this to Apple at the end of Aug 2020 and have since spent hours on the phone to them about this over a period of 4 months. They even replaced my watch at one point and the problem still occurred. I told them the issue was the link to car play and the watch/phone but they had me test lots of other things and report back but never tested the car play. Then just before Christmas they told me they were aware of the issue and the link to car play and developers were looking at it and an update would follow. They thanked me for all my time trialing things for them. This has become even more apparent in recent weeks when I have only drove the car once a week (lockdown) the watch works all week and stops working once I have been out in car. The only way to reset is to turn both the watch and the phone off and on again. The latest update 14.4 for phone and 7.3 for watch has not solved this problem. I drive a Mini Cooper SD.