in motion

The wheels are already in motion.

I want to see the scene in slow motion.

deIch möchte die Szene in Zeitlupe sehen. — samueldora

Never open the door of a car that's in motion.

ruНикогда не открывайте дверь автомобиля во время движения. — odexed

He put the machine in motion.

She put the machine in motion.