How to troubleshoot Audi 80's rough idle issue?

My Audi 80 has been experiencing a rough idle problem, where it shakes and vibrates a lot when stopped at a traffic light. What could be causing this issue and how can I fix it?

First, check and clean the air filter. A dirty air filter can cause the engine to run rough.

Another possible cause is a faulty sensor, such as the mass airflow sensor. Have it checked and replaced if needed.

It could also be an issue with the spark plugs or ignition system. Consider replacing them if they are worn out or damaged.