transmission problem

I have atrouble with my car (bmw 735i - 99 model) which can not be solved by our work shops in UAE , some times i can not get the 3rd,4th ... gear while driving,especially when the car is getting warmed after long period driving,I made computer check for the transmission , it dos not show any problem.
is there any body can help me , particulary german engineers.

THANKS ALOT