Every time I start the car and no one is in the passenger seat, the warning light comes on....doesn't happen when someone is sitting in the car...

 

Didn't they add a weight sensor in 06? I think it's just telling you that the passenger airbag is off because there's no weight in the seat. In the 05s you had to wire in a kit to deactivate the airbag life if a child would be sitting in the front seat and you weren't using the Porsche branded car seat. In 06 the weight sensor prevents the need for the kit.