2002 B5.5 v6 starting problems - throttle body?

This car has about 70K and has been properly maintained. Recently it has intermittent difficulty in starting. It has no codes. My mechanic replaced the temperature sending unit because it's cheap and he's had to replace it on most of the other vw/audi v6's that he maintains. It didn't help. He suspects a throttle body problem but recommends waiting until the engine check light indicates there is a code. He doubts I will be stranded with the car. (Usually it starts after several tries.) Anyone see this before?

Problem was the alarm system. Display in the dashboard often says the IMMOBILIZER was activated. Changing keys doesn't help. Dealer replaced "card reader" (RFID sensor?) in the dash. Repair was about $400 for parts and labor. I wonder if it would have helped to just reseat all the related electrical connectors, but anyway it's better now.