Your going to have find out where it’s eminating from. The most likely cause is the split seats rubbing together on the sides—felt between the two will eliminate it. Your car should still be under the bumper to bumper warranty. Figure out how to recreate the sound and take it in and show it to the service advisor.
Infiniti is good at fixing rattles and squeaks if they can reproduce it. When my car was new the cover in the front camera behind the rear view mirror was buzzing—I could reproduce it by lightly pounding I the front windshield. Showed it to the advisor who fixed it with self adhesive foam padding. A few days later they had me bring it back in because Infiniti sent an engineer to study the cause...that was a first! They replaced it with a new one.
I took my car to the dealer for oil change and brought to their attention about the squeaking noise. The dealer was unable to duplicate the issue and I had to schedule another appointment later this week and drove with technician. It was easy enough to replicate the noise this time.
The dealer was able to fix the squeaking noise by applying some lubricant on the hinges. The service adviser mentioned they usually apply lubricant if you go with full service with them. Interesting!
I had this same issue, the 2nd row single seat would squeak and rock back and forth a little bit. I have extended warranty and dealer said it was not covered and quoted me $2,500. I went on Craigslist and bought the whole 2nd row seats from someone parting out their QX60 for $250 and had the whole seat replaced by a mechanic for $50. I kept the old seat and took it apart to diagnose the issue and it came down to a bolt in the sliding track part that got a little loose.