Ever since my model 3 was new I've had a rattle tied to the front dash speaker grill. The rattle seems to be worse when the car is cold. I even had mobile service come out to investigate, but of course it didn't rattle. I ended up taking apart the entire dash trying to figure this out. What I realized (after applying sound deadening material, foam tape, etc) is that the grill itself was causing the rattling sound. What finally solved my issue was applying 1/2" thick neoprene foam weather sealing tape between the grill and the windshield (which you can barely see in the attached photo circled in red). That seems to dampen the vibrations that caused the rattle. Hopefully this will help others.