Hi guys and girls, I'm having this issue where when i start the car up and drive for a while it beeps and only one time. I'm just wondering what that beep is and would i have to worry about it. Thanks for any help.

 

no animation on the instrument cluster?

 

I have the same trouble with my 2001 A6T which I recently purchased. But my sound is more of a refined "whoop" than a beep. Mechanics claim never to have heard of such a thing, a salesman said it might be the turbo kicking in.
I did find a similar complaint on a Nissan web site and it was traced to the auto transmission switching from first to second gear. My noise only occurs on start up and ,like yours, it only happens the once.
I decided to see if it did the same using the Tiptronic manual gear change and sure enough - the car went from 1st to 2nd automatically but when I moved it into 3rd -- Whoop! I will mention it to my service dealer the next time.