Transmission Problems

I got a Lexus ES300 1994 and i started having transmission troble about 3 months ago I took it to the transmission shop they change that transmission 3 times and it wouldn't work, the transmission guy told me that it was going to be a electric problem a sensor probably so I took it to an electric he fool around with the car for about a week and a half and he couldn't get it to work.

When it started to have problems it wouldn't go in to 4th gear, then after all that the transmission & electric guys did the car would go on 1st and 2nd gear after that it loses the transmission then i have to turn off the engine and start it again and it would go again.

Does anyone has a clue about whats wrong with this car?