a4 odd idle

Hello all,

Knowing the breadth and depth of knowleldge in this group, I thought I'd ask here before taking her somewhere to potentially be ripped-off for not knowing enough about these things. If someone can enlighten me to the likeliest cause of my vehicle's malaise, you shall have an extra virgin of your choice when you get up to the big garage in the sky.

Anyway, a while back I obtained a 1997 Audi A4 1.8, yay for me. It's lovely (to me anyway) and still feels solid with 140k on it, but it has a bit of an idling problem. I have used my crap phone to try and capture this phenomenon:

That was sitting at idle and me revving to about 1500 (then starting to film) then letting go and not touching a thing thereafter. As you can see, the revs dip too far back then bounce around until finally settling where they should be after about 10 seconds. From idle, it does this with the slightest tap of the accelerator. It also does it from idle after only touching the brake. It never actually stalls, but gets mighty close sometimes before it bounces back up. Can occasionally be hesitant to the point of getting me killed when pulling away in 1st without slightly more than you'd think would be enough revs. The sound like some crazy back box is just the crapness of the phone.

Other than that, once it's moving it seems perfectly fine, decent power, smooth and quiet. Factory alarm has started going off for no reason recently, though the idle has been like this for waaaaaaay longer.

History is: A lack of servicing and due a major one, inc. timing. Previously driven like a taxi for 8 years whilst not actually being one (5th at 30, etc.). Doesn't seem to be leaking anything or burning anything it shouldn't be.

So, once it is serviced and timing bits are changed, should it come right or is this evidence of something more sinister?

Thankyou all very much.

Chandy