Reptiles cannot regulate their own body temperature, which makes the move about the animal's temperature control first and the glass tank second. Get the reptile into an insulated, temperature-monitored tub before you touch the enclosure itself.
Pro tip: Bring a backup heat source, like a second heat pack, in case the drive runs longer than expected; reptile temperature margins are tighter than most pets.
Watch out: A reptile exposed to temperatures outside its safe range for even a short time can go into dangerous stress or shock; monitor temperature constantly during transport.