A vacuum leak with throw an error code/light.
If it's not showing a check engine light and there are no codes, then it's a physical problem like low pressure from a failing fuel pump.
Mine showed the same symptom and I tracked it down to a leaking fuel hose inside the tank where it attached to the pump.
Check the fuel pressure and the bleed down rate after the engine is off. It should hold pressure for a bit.
https://xoutpost.com/bmw-sav-forums/...leaking-2.html