My 99 Ram had the same symptom and the ABS light also came on. Mine had a bad speed sensor in the rear axle housing. Easy to fix. Same thing happened on my '00 Chrysler but this one was on the trans. Even easier fix.

I agree the Neons had a speedo problem that wasn't a speed sensor. It was also intermittent. My mother had one that did this. When I gave the car to a friend he found the fix online and repaired it rather quickly and now it's fine.