First that pops to mind to try is to loosen and retighten the fender bolts and see what it does after that. If you don't already; consider taking it offroad or somewhere that twists the body a bit. You may get some popping and be able to narrow it down or maybe relieve whatever is sticking.

^that sounds like a good start

My 2000 Sport is making this same "POP" in the left side of the dash too. Seems to be right under the windshield. Usually happens after startup. Will do it while driving AND not in drive. Mysterious

My main suspicions lead to the suspension, or ALSO, the driver front tire that slowly loses air. All of the above guesses and suggestions do not make a difference. Twisting the body, different temps, etc, have no affect on the noice and frequency of the noise. It's consistent on scaring the **** out of me after startup

Fascinating.

I wonder if an occasional loud pop could be caused by a binding speedometer cable, or the mechanical connection it shares with the cluster.

I can toss my name in the hat on this one too, lol. Mine does every now and then, usually when it's cold and I hit a big dip/bump. Sounds like plastic popping.

I wouldnt quite call the sound a pop. Mine sounds more like a cracking noise. But every panel on my Jeep makes noise so I really dont care haha

Very unlikely to be suspension since it does it sitting still and a tire only pops once so rule that out. My guess would be something in the exhaust that as it expands it pops, I'm guessing exhaust manifold. Next time you start up open the hood and listen from outside to see if you can hear it and can isolate it.