Jookie seems to be spot on...
I don't know much about vehicles, certainly not as much as many people on this board, but I've had the same problem with my 80's oldsmobile. I had to get into the throttle body & clean it out, put it all back together, and it worked like new.
At first it sputtered & the RPMs fluctuated a bit, but after running for about 30 seconds it jumped right to where it should be and haven't had a problem since.