Does anyone else have this problem?

I have a 2000 Stratus, 2.4 L, with an automatic transmission. Ever since I bought it new in Dec. of `99, I have had a problem with the acceleration fluctuating when I "get on it." It acts like it is kicking in and out of low gear..it's like whaaaah..ugggggghh, whaaaah, uggghh. The first time this happened I almost got ran over by a semi while entering traffic on I-44.

Is anyone familiar with this? If anyone has had this problem and knows how to eliminate it, please let me know. Any and all responses will be greatly appreciated. Thanks