Hard to start after refueling
 

My 82 year old father owns a 2003 Jetta GL 2.0 L
The car starts fine all the time except when he stops at the gas station & refuels it.
When he tries to start the car after refueling, it acts as if it is flooded. He has to crank it for awhile before it starts.
Does this make sense to anyone? What do you think is causing this?
The service engine light is lit on the dash but ever time he takes the car into the stealer, they say it should be fine now but won't tell him what the code is.
Thanking you for your assistance.