BMW X3, 2004 Automatic transmission shifting issues

[JCL]

First check is whether the fluid level is correct, as low fluid level can cause shifting problems. Look for obvious signs of fluid leakage around the transmission.

While the fluid can be changed, there are two schools of thought. Replacing fluid adds new fluid that by design has a high level of detergent in it. That can clean out the transmission, and since there isn't anywhere for the residue to go, it can cause problems in the valve body which has lots of small passages and check valves. Transmission failures can be precipated by changing the fluid in a transmission that is otherwise fine, expecially at higher mileage.

Others feel that clean fluid is better than dirty fluid, and that all transmissions that fail after a fluid change were about to fail anyway.

If the fluid level is correct, and the shifting problem is enough to be noticeable, then you can always decide to change the fluid based on not having anything to lose. I would probably do that myself. If a fluid change doesn't have any effect, take it to a transmission specialist for diagnosis. Your dealer doesn't repair transmissions, so you would need to find an independent that you trust.