Here in the midst of a giant snow storm in Wash, DC, my '98 528 sport failed to start for the first time, even though it's not really that cold. The symptoms are somewhat strange.
I had driven the car the day before with no problems. Around 4 pm, the car was sitting in my driveway but the alarm spontaneously went off. The key remote "unlock/lock" buttons had no effect. After about a minute, the alarm stopped. When I opened the door, the alarm went off again. This went on a few more times and I left the car in disbelief. A few minutes later, I went back to the car and everything seemed fine and the remote worked perfectly. However, when I tried to start the car it wouldn't start. Even though there was enough power for lights, remote, etc., there didn't seem to be enough juice for the starter motor.
BMW roadside assistance came and gave me a jump and it started immediately. I drove it to the dealer, Heishman, in Arlington, VA, and left it (after hours). Unfortunately, they haven't been able to get to it for the last two days.