I have a vw jetta that will not start right away after filling up with gas. on 2006 Volkswagen Jetta

Everytime I get gas it won't start, cap is on tight. I have had it towed to a shop, just to have them drive it off the wrecker. Had the mechanic cometo station yesterday and by the time he got there it started fine for him. He can't find anything wrong. please help!

Asked by for the 2006 Volkswagen Jetta
The light is on but goes off when it starts back up.
have your codes read to see if there are any. then post so we can advise. does yhis happen only when you fill it all the way up or anytime you add gas?