Sounds to me like a radio glitch. Normally anytime a heli or airplane for that matter does real quick jerky movements on its own, its usually the result of interference.

Untie the antenna from the landing skids, and arrange it where its more exposed. There are a couple of methods of doing this.

Wrap it around a straw, or even let it hang down. Just make sure it doesnt get into the rotors.

Also make sure your transmitter antenna is fully extended. Dont point the antenna at the helicopter as there is a "dead" zone near the tip of the antenna.