cdahms

My wife was driving home the other day and came to a stop sign. When she pushed on the gas the engine would rev up but the vehicle would only crawl forward very slow. It would do this until you reached about 5 mph then the vehicle and transmission appeared to be fine and shift correctley. Accelerating from a stopped position is the only problem I am experiencing, no matter if I put the vehicle in 1, 2, 3, or D. It does the same thing over and over again. Reverse works fine. I finally got the trailblazer home and unhooked the battery to reset the codes. After I did that the trailblazer was running back to normal for a couple of days, approx. about 40 - 50 miles, then it started to act up again by not wanting to accelerate. Any ideas????????