1994 Chrysler LHS

Not sure what the cause is, but this exact thing happened to my friend's '93 Caravan with 190,000 miles on the original transmission. You didn't list the mileage, but if it's relatively high, there could be a sticking valve in the solenoid pack or a seal leaking in one of the clutch packs. My friend added a can of something which solved the problem. The name "Sea Foam" comes to mind. I've heard of it but never used it. Ask the folks at the auto parts store for an additive that can be left in the transmission. There are cleaners that are meant to be drained out shortly after adding them as part of a fluid and filter change. That's not what you want to add.

Caradiodoc