That sounds dangerous ... it'd be a real issue if you were waiting for traffic to clear before turning and the engine restarted BUT the transmission went to NEUTRAL. Instead of waiting for a dealer call back I would immediately drive to and have the dealer service center investigate and until resolved request a replacement loaner car as this is a VERY DANGEROUS SITUATION!!
Meantime I recommend you turn OFF "AUTO STOP/START" or drive in SPORT (That defeats auto stop-start).
My opinions are free - you'll get exactly what you pay for!
1998 Z3 2.8
2007 Rav4 V-6 AWD