I have the same problem with airpods pro 2.
When an incoming call comes in, the headphones seem to automatically connect to the phone. Alternately, the transparency modes are arbitrarily turned on for a second each, then noise reduction. It takes 12-15 seconds for normal operation.
There is no such problem when making an outgoing call.
All other functions work perfectly.
The recommended reset of the headphones did not help.
Tried all possible manipulations with the phone. Even flashing via DFU did not work. I have an iphone xs max. Before that, there were no problems with connecting any bluetooth devices. There are no such problems with the headphones on my wife's phone.