1991 LeBaron Convertible Seems to Drop into Second or Third

[Lebaron1991EC]

I have a 1991 Chrysler LeBaron convertible and when I drive it sometimes it seems to drop into second or third gear. It will have a significant down shift and the engine will seem to Rev. I can get the car to go faster, but not easily. I turn off the car and restart it and then it's fine until it happens again. I dare not take it on the highway.

Has anyone experienced this? Does anyone know how to fix this? It doesn't seem like the transmission although it may be.