Why does my shifter get stuck?

Not sure about a shift lever being stuck moving from drive to park, but from park to drive if the shift interlock mechanism is not released, it will stay stuck in park. If the shift lever interlock is not releasing, it could be due to a faulty brake light switch or related wiring. See if the brake lights work all the time for a quick and easy indication of whether or not this could be a source of the problem for you. The same switch that turns the brake lights on when you depress the brake pedal also releases the shift lever interlock mechanism.