I would get it scanned by dealer or an independent with a proper scanner to assess. No sense chasing every possible thing that it could be. One good scan should tell you the issue and point you in the right direction. Bad sensor, angle sensor, ABS unit, etc. You could try cleaning the sensors and the rings off, but before buying parts or throwing money at it, get it scanned.
Fixing your steering wheel dead centre is just getting a proper alignment done. I've had best luck at the dealer. I also set my rear toe to near zero toe in (0.02 total). This save the rear tires from excessive wear, but it is outside of BMW spec. They don't mind as long as I pay the bill and sign off on it
