Hello. That does not really sound like a problem. I have had cars like that in the past that would roll back if no acceleration was given and foot was removed from brakes.

However, do know that these things are well known for transmission problems. I had a 95' Chrysler Concorde that had tranny problems when it had only 85K miles and currently my aunts 98' Plymouth Grand Voyager minivan has transmission problems and it only has 88K miles. Seems like they rarely make it beyond 100K (at least the 99' and older models).

Just keep a close check on it.

Good luck.

1985 Mercedes 380SE
1973 Pontiac Grand Ville
1969 Chevrolet Caprice
1989 Pontiac Safari