Automatic transmisson

Sounds like you have a computer-controlled transmission. The computer learns the characteristics of the wear in the clutch packs and updates the shift schedules to maintain a nice crisp shift. That memory was lost when the battery was disconnected. If your system is like the Chrysler system, there was likely some slippage during a shift so the transmission went to a default condition that allows you to drive slowly to a repair shop. Your computer has to relearn the shift characteristics. There's a good chance that relearn procedure is partly completed and once you turn the ignition switch off and restart the engine, that will take it out of the default mode. The slippage during shifts will likely disappear shortly and it will stop going into default.

If this continues it's time to visit a transmission specialist. They will connect a scanner to read the stored diagnostic fault codes in the Transmission Computer, then they will be able to suggest a course of action. In the meantime, one thing you might try is accelerating harder than normal, then letting off the gas just as it is about to shift into the gear where the problem occurs. This would be similar to easing up on the pedals just when you want to shift your bicycle to a different gear. The reduced torque will prevent any slippage in the clutch packs. Once firmly locked in gear, you can accelerate again. If slippage really is the problem, this trick will often allow you to get to all the gears and be able to drive on the highway until you can get to a repair shop. If the problem still acts the same way, there could be a sensor problem or, rather than clutch plate wear, the slippage could be due to a leaking seal in one of the clutch packs. That would cause the slippage to continue as long as it is in that gear, not just as it's going into that gear.