What is the cause of a rattling noise in my BMW 1 Series engine?

I have noticed a rattling noise coming from my BMW 1 Series engine. It only happens when the car is idling and goes away when I accelerate. What could be causing this and how can I fix it?

The most common cause of a rattling noise in your BMW 1 Series engine is a loose heat shield or exhaust pipe. It's important to have this checked and repaired as soon as possible, as it could lead to further damage if left untreated.

Another possible cause could be a worn or loose belt in the engine. This can also cause a rattling noise at idle. It's best to have a mechanic check the belts and replace them if necessary.