Transmission Problem With Idle Problems

[wendo240sx]

I have a 91 240sx that is having transmission problems and idle problems. When the car is idling stopped, the idle will go up and down. When the car is running on the highway, the transmission will not shift smoothly, and the RPM will increase up on its own without pressing more on the gas pedal. Sometimes when stopped at a red light, car will start shaking and turn off sometimes. Even when reversing car will shake and turn off sometimes. Please help...