I guess just try leaving BT on before starting vehicle. I have both an older gen BT ULF in the older E46 and newer in the E83 and they both function just fine. If for some reason I've updated OS on HTC or updated MS Mobile telephone then the older ULF has the most issues (time of pairing) with the phone; onced paired and phonebook/SMS initially transferred all is well.

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E83 - Aero PKG Mods installed: Homelink mirror. CIS-IBUS video module, AUX, Rr Dr Release, stock wheels, Remote start, CarPC (Atom) & mud flaps - NAV - MKIV - NA Map DVD - 2011
E46 - 18.5 wheels/tires (summer), 17 stock (winter), Homelink, NAV software upgrade, BMW video module, Radio to V53, AUX, USB IBUS interface,BMW alarm install, CarPC(Epia), remote starter, tank battery & angel eyes. NAV - MKIII - NA Map CD - High Version 2008.1