That's right! The snakes over the heater move because hot air rises and move the snakes. The snakes in the middle of the room have no moving air under them so they stay still.
The next experiment we tried was holding a table tennis ball over a hair dryer. The rising hot air keeps the ball floating in the air. The experiment doesn't work with a heavy bouncy ball (too heavy for the air to lift) and with a light foam ball (too light to stay in the warm air flow so it gets knocked over very quickly).