My 2018 accord EX-L started with a rattling noise between the rear deck and rear glass when on the highway. i placed some foam in between and that's that. Now i have a random rattling noise inside the dash above the glove compartment, and at times when i make a turn it sounds like a piece is actually moving back and forth when i turn then it stops. Took the car to the dealer and found nothing wrong. i believe the mechanism that pushes the air out to the vents has an issue because when ever the rattling starts randomly i start pushing the the air flow button repeatedly to change the air flow in different directions thus by opening and closing the shutters to move the air around and it seems to stop the noise. that issue also affect the ac where is not as cold and the fan speed become week eg: fan speed on 2, you have to raise the fan another notch to feel the air. whenever i turn ON the ac and it's as cold as it should be i know the shutters inside the is not closing properly and eventually after a while fan speed become normal and ac is like arctic air. So, if anyone has any suggestions feel free to share because it is really annoying for a brand new car.