Front passenger door rattle while closing with window down

I recently noticed some metallic sound, like metal items brushing each other while closing the door. The noise comes up only when window glass is down. Typically, I keep my windows closed and hence did not notice this previously. Planning to take it service center in coming week. I am grateful for any inputs on this issue. I wanted to have some insight before heading to the VW authorized service.
I am from Bangalore, India and the car is under warranty. Also, any insights on how this issue occurs and is there anything that I need to be mindful about?

Thanks in advance!