[Allworth]

There is no such thing as stop start motor. Starter motor is used to start a car regardless if button is being pushed physically or it is being used by start/stop system. Normally when battery charge is low, start/stop is suspended without any warning, if voltage goes drastically low it will give a warning on battery voltage, so I agree it has nothing to do with a battery. Then; ambient temperature must be above 3C, engine coolant above 60C, vehicle not reversed before stopping, driver seatbelt fastened, vehicle speed - 0 km/h. There are many sensors...

I would have started with a computer diagnostic to track an issue.
I do always carry $40 diagnostic tool that of a size of a matches box and connects to a smartphone this works with all BMWs.