My 2007 Crown Victoria isnt shifting correctly..... i think

I just purchased an ex police car 2007 crown victoria. The car ran perfectly
until just yesterday when it started to shift differently when coming off a stop.
It felt like the car was in neutral and then it kicking into first and continued
accelerating like normal. It also happens when i change the gear from park
to drive, it takes a second for the car to accelerate then theres the kick. My
friend thinks it can be the torque converter but im not sure what it can be.
Also i think it may be something to do with the overdrive because when i turn
it off it rarely does the things from above.