After fuel fill-up strong gas smell when car left in garage--what is cause.? on 2006 Mercedes-Benz E350

It only does it after each fill-up and last until a few gallons of gas have be used

Asked by for the 2006 Mercedes-Benz E350
Sounds like you have a seal at the top of tank area that is leaking, may be the fuel sender/fuel pump seal, has worn out and cracked, when fill and drive the gas sloshes and leaks out and causes the smell till enough fuel is used to lower the level where slosh is minimal. Take to shop for repair ASAP. Fuel leak is nothing to wait on.