Why does my Audi A5 engine make rattling noises while idling?

I have noticed that when I am stopped at a red light or in heavy traffic, my Audi A5's engine starts making strange rattling noises. It's only been happening recently and it seems to go away once I start driving again. What could be causing this issue? Any suggestions or advice would be greatly appreciated.

This could potentially be a sign of a worn out serpentine belt or tensioner. It is best to have a mechanic inspect and possibly replace these parts to prevent further damage to your engine.