I just bought a 2007 F150. I noticed when the truck is cold, it sounds like there is a poping / rattle noise coming from the center dash just under where the tray is on top of the dash. I can't figure out what it is!

I have diagnosed it is not the radio or HVAC (i think) - I have had both of them off and still heard the noise. I can turn the truck to the 'On' posistion without starting it and it still makes the noise. The noise doesn't change when the car is started or moving down the road. The noise goes away after about 5-10 mins of driving. Any thoughts?