I took it back to the dealer several months ago (just 1-2 months after I got the truck). They test drove the truck and they believed it's the sunroof, so they ordered a new sunroof piece. And it took them 3 days to remove the ceiling, the headliner, sunroof, all side panels inside the truck, etc.

It's quiet for 1-2 months, and now it's coming back again, and it's making two noises. One from the end of the sunroof when the truck is rolling, swinging, etc. It makes noise as if the sunroof has been squeezed. The other from the end of the sunroof on the driver side every time the truck is moving (and even when idling sometimes) on not-so-perfect roads. It sounds like a plastic panel is not screwed tight.

I had another dealer look at it, and they believed it's the rails that are making the noise. I will bring it back to the original dealer and show them a print-out of this article. Thanks guys.