Not sure about the Auto Start Stop Function function, but from doing a little digging
A clever way to save fuel: the Auto Start Stop function turns off the engine each time the vehicle comes to a complete halt - such as at traffic lights - and restarts it automatically. A reduction in fuel consumption is the result.
The principle is simple: if the engine is not running, it cannot consume fuel. The Auto Start Stop function turns off the engine whenever it is not needed. In a traffic jam or in stop-and-go traffic, simply putting your BMW into neutral and taking your foot from the clutch will activate the function. "Start Stop" on the Info Display signals that the engine has been turned off.
To set off again, just put your BMW back into gear: the moment you depress the clutch, the engine immediately springs back to life and you can drive on without a moment's delay.
Driving comfort and driving safety are not affected by the Auto Start Stop function. The function is not activated, for example, until the engine has reached the ideal running temperature. The same applies if the air conditioner has not yet brought the cabin to the desired temperature, if the battery is not adequately charged or if the driver moves the steering wheel.
The Auto Start Stop function is coordinated by a central control unit that monitors data from all relevant sensors, the starter motor and the alternator. If necessary for comfort or safety, the control unit will automatically restart the engine: for example, if the vehicle begins to roll, the battery charge falls too low or condensation forms on the windscreen.
Furthermore, the system also recognises the difference between a temporary stop and the end of the trip. It will not restart the engine if driver's seatbelt is undone, or if the door or bonnet is open. If desired, the Auto Start Stop function can be completely deactivated with the press of a button.
When used consistently, the Auto Start Stop function delivers significant reductions in fuel consumption and CO2 emissions.
As long as I can permanently disable it if I don't like it, I don't mind them including it.