No, you do not have air in your gas line.
But–how do you fill up the tank?
Do you stop when the pump clicks off for the first time?
Or, do you do the click-click-click maneuver to force additional gas into the tank?
If your answer is the latter of the two situations, then I suspect that you have contaminated the evaporative emission system’s carbon canister. Or, you might have a defective purge valve in the evap system.