[Vikingstaff]

Not to offer up something you may have checked already, but I see two possibilities here:

(1) Could be the turbo lag mentioned above. IF newer to a well tuned turbo vehicle, it can throw someone off at first. However, based on your description of the problem, I think it could be #2 below:

(2) Does your X3 have the auto motor off feature at stops? My 2017 does. Default setting is turned on. Motor turns off when you come to a complete stop to save on fuel. Turns back on when you push on the gas pedal. However, there is a noticeable delay to “restart” the actual motor.

To disengage or turn off this fuel efficiency feature, you have to push the button (attached picture, button in circles the push start button - labeled “A Off”).

It helps save gas, BUT produces the exact effect you mention: delayed motor/vehicle start from a dead stop. I found it VERY irritating, and keep it off. If I wanted to maximize fuel efficiency I’d drive my wife’s hybrid, and not have a turbo BMW…lol My contribution to fuel efficiency was switching from a 6.2 L V8 to this Turbo 4. Not interested in going further in compromising performance.