patrol 1994

hi there, first time user here.
i have a 1994patrol on petrol and yes its thirsty but that was to be expected. i am hoping someone may have a suggestion as the few mechanics did not know or could not be bothered. i think its a transmission problem, its an auto. it goes well when first driving around for half hour or so then if i stop and turn the car off for 10 minutes and then get back in and get going the problem starts. firsly it will rev out higher in first then really jump into second and really rev hard like i have selected second gear only. if i catch the red light i get worried as it gets very jumpy at idle reving up to 12/1300 then down then up and the bloke beside me thinks i want to drag him. i get going and under accelaration the car chugs along. its like there is no go and the tacho just drops and then all of a sudden it gets power again then drops then goes then drops and so on and this happens on freeways doing 100ks also and i have to slow down to about 50ks which is a bit scary. it chugs along for a few minutes and then its running good as gold again but i dare not stop and turn the car of for a while or it happens all again. if any one has heard of this happening please post me as i would really appreciate it so i could get it fixed as apart from that the car is great.
thank you all
Rod from Melbourne