2006 Volkswagen Passat Rattling noice

Hello there,

I have a 2006 volkswagon passat at almost 30,000 mileage. When I start the car up, there is a large rattling noise and when it runs for a little bit, it stops. But then when Im driving I can still here the rattling noise from time to time. Can you please tell me, what might be the problem and where I should take it too. I don't want to go the the dealership because they charge outrageously very everything. Thank you, and have a good day.