2001 4.4 X5 DOESN'T UP-SHIFT TO HIGH GEAR AT TIMES
 

When starting out it will shift up but, not all the time. Warm or cold engine Temp. or ambiant Temp. doesn't have a thing to do with how it acts.
The longest it works correctly is about 30 Min. or so.
Can anyone help?
Fuzzy

First thing to do would be do a drain and fill on the transmission pan. That will show you the condition of the fluid, and ensure you are at the proper level when refilled. It does sound like you may be low on fluid possibly.