I started to hear a noise similar to what you're describing after I replaced my thrust arms, but didn't really pay attention.

Does the sound seem to come from a certain side, driver's or passenger's?

the "pop" or empty like metal sound comes from front passanger side. It's almost like coming from front axcel.

Do a quick test.
Get under the car and locate where front drive shaft goes into an enclosure (right under driver seat area.)
Move the shaft up and down. You should have very little play. My had about an 1" of travel.

The noise I'm hearing definitely comes from the driver's side. I looked to see if I could locate the driveshaft under the drivers seat, but I couldn't see anything that I could reach without jacking the car up. I will try again the next time I change the oil. Btw, I just turned 80k, so I'd like to think it's too early for TC problems, but who knows.

Look for a cross member under the car.
Locate front drive shaft (between front axle and transfer case)

2008 BMW X Series (E53,E70,E71,E83) X5 4.8i 4-WHEEL drive SHAFT/INSERT nut

In the image above, part #2 is where the problem is on the "U" join section.
Check for play, it is accessible without lifting the car, if you are thin enough.

Good luck.

Who knows?? I knows!
My 2012 50i is at the dealer now getting a new transfer case at 45k miles.
I noticed some "crabbing" of the wheels in tighter turns, and parking scenarios. Like they weren't all able to turn at the same speed. Then I got new tires and it seemed to go away, for a while.
When it returned I noticed, and when the vehicle went in to the dealer for some recall work I mentioned it. Luckily I have ~6 months left on my CPO warranty so it will be on BMW.

My 35D had some shudder during tight turns under power, BMW quoted $5000 or so for replacing the TC. Elsewhere in the forum I saw someone had changed the TC fluid and got reprogramming/adaptation cycle run and that fixed it. I decided to try that and luckily it worked for me too. From what i can gather the plastic gear in the actuator wears out, replacing that and changing the fluid seems to fix the issue. Her's the link to the thread.

https://xoutpost.com/bmw-sav-forums/...4bdc-4a14.html

Here is a plastic/cf blend aftermarket solution for the servo actuator gear -

https://www.ebay.com/itm/For-BMW-X3-...-/221576643880

http://x8r-instructions.co.uk/BMW-X3...o-Actuator.pdf