Why does my Audi A4's engine make a rattling noise on cold starts?

I've noticed that my Audi A4's engine makes a loud rattling noise when I start it up on cold mornings. Is this normal, or should I be concerned?

The rattling noise on cold starts is a common issue with Audi A4 engines, particularly in colder climates. It is caused by the tensioner or timing chain becoming loose when the engine is cold. This can be fixed by replacing the tensioner or doing a timing chain adjustment.