Yep, mine is exactly like that. Will do it the first startup of the day, and sometimes when I give it some gas trying to back up a hill.I took it in this week for maintenance and let the dealer know it was still happening. They have yet to figure it out. It is much more noticeable than a heat shield. It can be felt through the entire vehicle. They asked to keep it to try and figure it out. They are just as puzzled as I am. The really tough part is that it only pops on the first startup of the day. They literally have 2 seconds to locate it. They have it on a rack and several mechanics stand under to try and find it. This does not seem to impact how it performs or drives. It is Jeeps way of just aggravating me to death because issues like this make me insane.