You have to learn how to be still on camera. 

Observe how you are still in life. 

Often, while acting your moving because you’re resetting or dropping out. It is you, the actor, and not the character who is moving - a movement of self-consciousness. 

Observe when you’re doing that and learn how to stay in.

Movement can be distracting. It can dissipate your energy. When you listen you are usually still. Half of screen time is the reverse—where the other actor is listening. 

The listening actor is us, the audience, listening. She is looking at the speaking actor, listening and so are we.

The young football (soccer) player can run at great speed. He can go. But to become excellent he must learn to stop. Once he is stopped then he can start again. 

The lion as it waits for its prey is stock still yet alert mentally, breathing fully and calm. That belly going in and out seems contradictory to the animal not moving.

Take that image back to your acting. 

Stillness doesn’t mean locked. The lion is still yet breathing fully and it’s brain alert. 

Find your stillness by being on your breath and having space in your mind and if your physiology needs movement there is the useful tic or twitch.

Watch you don’t succumb to that actor’s voice ‘I should be doing more.’ and start movements to try and be interesting or good. If you’re in the scene, in the space, time moving forward, you’re the character, plot moving forward – that’s enough.

You have so much power to release and stillness is a state to do that from.