I need help. on 1999 Jeep Wrangler

I have A 99 Jeep Wrangler with a auto transmission stright 6. When I start it up and take off in gear the rmp's rev up real high then it takes it a while and then takes off good. The more u drive it the better it starts working. Then all of a suddend going the same speed it drops down in speed revs up real high then will take off.. Any answers??

Asked by for the 1999 Jeep Wrangler
check your fluid level if ok then take to trans shop for diag