I have a MY00 A5 Avant 2.4 (UK spec). Occasionally when I start the car I will hear four short beeps from inside the rear right hand wheelarch. This happens within about 10 seconds of the car starting. It happens only occasionally (perhaps once a month). The car exhibits no other problems at all and I have no warning lights or indication. Could it be the alarm which is not seeing a contact or something like that?
Thanks, Dane.

I've been noticing the same thing for the past few weeks. Also, this morning, after not running for 3 days, my engine would not turn over. I'm guessing that I simply need a new battery, and those beeps were basically telling me the same thing. Be back in 2 hours or so, gotta get a ride to buy one-

ps- my first post

I think your on the right track with the alarm being the cause. There is a battery inside the alarm horn to make sure it goes off even if power is removed to the horn. You may have a bad connection between the alarm module and the horn itself. They will also beep by themselvs if the battery level in the horn is too low.

No more beeps for me...new battery