About an hour later, it won't even start again. Will try to jump start it again tomorrow morning and drive the car to the dealer.

 

Does the car sometimes have this problem and then occasionally start as if nothing is wrong?

I am trying to track a similar sounding issue, but it has been intermittent for the past year.
https://5series.net/forums/topic/106...5#entry1265035

Keep us posted on the outcome

 

Okay, found out the problem--notthing major but kind of unexpected off-the wall.

Starter is fine
Battery is great



Looking at the picture, the big red wire cable attach under the metal plate of the positive post. I guess there were dirt and some corrosion underneath the metal plate. The red cable wire goes to the starter! Apparently when I jump started the car, the jumper cable made better contact to overcome the resistance (dirt & corrosion) and power the starter.

For anybody looking to jump-start, the negative post is to the right of the positive. The "negative chasis bolt" is that big hexagon nut.