Mercedes E200 petrol, 124 model, 1994 year

Question

I have an E200, petrol, automatic, W124, built in 1994. Recently I encountered a problem with the revs of the car. The revs are not stable. The car might start and switch off or start at low revs and when the engine is loaded with e.g. with the ac or power steering and the gear the car will switch off. When started again it might do the same or start at high revs of 1500. When at 1500 it will not adjust and is pretty dangerous to stop as it will behave like the petrol is pressed at the same time that the brakes are applied. When switched off and on sometimes it resets to normal revs but still does not behave normally. My mechanic suggested a throttle replacement. Is there anything else that might cause that? like a wiring problem or vacuum tubes? Can the throttle be repaired ?  Thanks for spending time reading about my problem.