1994 Pontiac Sunbird Transmission vibration.

Hi to all.
I am new here and I am from israel so sorry about the spelling mistake.
My problem is strange - After I drive with the car at least 40 minute/10-20 KM and come to a red traffic light and I need to slow down, at low speed my car start to vibration, the same like if you stop the car with manualy transmission at first gear integrated.
If I am not put the transmission handle to N the engine is turn off.
I can restart the engine at P or N and everything is O.K.
The second I shift to R or D/2/1 the engine is turn off.
If I wait half an hour everything is o.K until the next half hour afterward.
My garage mechanic person said that I need a new transmission and he do not know what is the problem.
i look at few forums in israel and few guys got the same problem without a solution.
Some guys said to me to disconnect the Torque sensor that come from the radiator side.

Can you help me?

regards,

ALON