Kilgore, have the electrical system checked out - especially the IBS (intelligent battery sensor). I had the battery low warning on my CPO '07 E91 (original battery, ca. 37,000 miles), followed by the car stalling going around a slow corner.
Dealer found nothing wrong until they tried to move the car at which point it wouldn't start. When it did start, the alternator was charging at 17+ volts. Alternator was replaced. Dealer said that sometimes happens on the 7 series but is uncommon for an E9x.
A few weeks later, the Low Battery warning came up again - new alternator found to be overcharging at 15+ volts, replaced again.
Two weeks later, with the car in for unrelated service (and no more dash warnings), I luckily asked them to check the charging system. Sure enough, the alternator was again overcharging and this time they checked the IBS unit which was found to have an intermittent fault (first time my dealership had encountered this problem - ain't it fun being a guinea pig?).
Battery cable and offending IBS unit replaced and all has been fine for the past 4,000 miles. Glad the car was under warranty as alternators are something like $900 a shot!
Let us know what happens with your wagon.