I'd check the following:
1. Fluid level....
2. Replase TSS (Turbine Speed Sensor)
If you still have the problem, for 35 dollars purchase a transgo shift correction kit and install it as SOON as possile. Once installed, I'd perform a power flush.
At this point if you still have a problem, I'd check for any codes.....
If no codes, I'd check your engine coolant temp sensor..not the one for the gauge but the one that sends signal to PCM for controlling transmission shift, etc....
Bob
