I own a 99 A6 quattro and I noticed that when the car is cold it starts right away, but after I drive it and it warms up, if i have to shut it off, it tends to start hard after is warmed. There are no codes or lights on. Any one knows what could be the cause of it ?

 

Change your coolant temp sensor. Its on the back of the engine on the passenger's side.

 

How involved is that job ? Do I have to remove any thing to see it , and what does it look like ?