I have a manual 2008 B8 A4, with the 1.8 turbo 160ps engine.

The problem is it jerks a bit, so for example, in 1st or 2nd gear, if I am cruising at slow speeds around the 2,000rpm range it gives of a constant jerk.

What could this be?
The car has almost 19,000km.
Servicing has been limited to only oil changes so far.

 

Anyone?

I also noticed that when launching at around 1,200rpm it vibrates. If I launch at 1,500rpm or more there are no vibrations

 

I think you have to keep the car at least 2,000 rpm to keep the 3,500lb thing moving with the 1.8t engine because the engine has much less power below 2,000 rpm.

As for the constant jerk, you'll need to check on spark plugs (I recommend NGK for best performance)

Mass Air Flow sensor (MAF) I don't think it'll die so quick.
Air filter.

For anything bigger than that, like vaccum lines, etc. bring it to the dealer for warranty.

 

Although your car is close to brand new, I had a same symptom at low throttle and was caused by low on ATF.