2.7tdi rattle when idling and in 1st

Afternoon folks, hope everyone is well in the A6 world. I have a 2006 2.7 Tdi and on start up, and when idling, there’s a slight rattle from the engine, which goes when revving and when driving it normally disappears after going up through the gears  - has anyone come across this at all? There’s no warning ⚠️ lights and the car drives absolutely great as per, but I’d like to know if it’s a common thing and of course what I can investigate. Thank you ok in advance.