Rattling at idle

[Bluematteo22]

Hi I’m new to this forum last week I purchased a  2016 SQ5 TDI PLUS from an Audi dealership however I soon noticed it was making a rattling noise at idle about 700RPM at 800 RPM it is gone ..I took it back to Audi who said yes it is rattling we can’t find it but it is not detrimental to the car and said they could do no more... anyone got any ideas what it could be it’s driving me potty... it sounds like a trim or a cable loose 

Cheers