Low battery after start is a common problem in the 8 and in the E32 740 that I had.
They start ok. But the battery voltage after the vigorous battery usage turning the starter is too low for the electronics.
Most common first sign of battery problems is the "Trans Prog" message and a shift into transmission safe mode. Random messages then follow.
If you drive the car a ways the messages go away as the alternator brings the voltage back up. Warm starts don't commopnly stress the battery any where near as bad either.
A load test is the only way to check if the battery has enough voltage left after cranking.