tranny shifting problem

i have a 95 k2500 and when i am driving it it will shift into second with no problem but it wont shift to 3rd or od until i let go of the throttle then it will shift smoothly into od, then when i press the throttle it will jump back into second and it wont shift until i let go of the throttle and it will keep doing that until i let it sit for a while or unhook the battery for like 10 secs. then it will just work fine it happened to me three times. the first time i let it sit over night and it worked fine for about 4 months. then it did it again and i unhooked the battery and it worked fine for about three days and now today it did it this morning and i let it sit for about four hours and now it works fine i cant figure it out