xsrao

Hi, I just got my new Audi A4 last week. I found something different from my previous car. The symptom is as below. After engine cold start, it shows high rpm around 1200. The car is vibrating and a bit noisy. Only after around 25 seconds (is this very long?), rpm drops back to 800 and the car stops vibration and becomes quiet. Is this normal? Can any expert help? Thanks.