Thanks again Braumin.
I have now been driving the car for two days with outside temperatures being under 20 degrees and have not had one problem at all. In fact, just as a test, I have been driving with driver and passenger seat heaters on as well as rear defroster on to see if a high load would trigger any problems but the car has just been fine. No problems.
Don't know why the seat heater and defroster on this past Friday afternoon caused a problem because I would think that the car's electrical system should be able to handle this load which has never been excessive with any other BMW or other brand vehicle I have owned. But apparently it did not handle the load so I think that you must be correct.
I will cancel appointment with dealer as you suggested and turn on electrical components in stages as well as keeping car on tender more often when weather is severely cold.
You have been truly helpful and I sincerely appreciate your input.