Why does my Audi's engine make a rattling noise when starting up?

I have noticed that my Audi sometimes makes a rattling noise when I start the engine. What could be causing this and is it something I should be worried about?

The most likely cause of the rattling noise is a faulty timing chain tensioner. This is a common issue with Audis and can lead to serious engine damage if not addressed. It is recommended to have a mechanic inspect and replace the tensioner if needed.