Why does my Audi A4 make a clicking noise when I turn the key?

Whenever I turn the key in my Audi A4, I hear a loud clicking noise coming from the engine. It seems to happen more when the car has been sitting for a while. What could be causing this and how can I fix it?

The most likely cause of the clicking noise is a low battery. As the battery loses charge, it may not have enough power to start the engine, causing the clicking noise. You should check the battery and make sure it is fully charged. If this doesn't solve the issue, there may be a problem with the starter.