Do not deliberately do anything but breath In and Out. Do not move the hands or feet or adjust the posture in any way. Do not twitch. The phenomena are different for different people, and do not occur with all people. Some people experience twitching in the legs.
Some people experience twitching in the buttocks like the body wants to hop around.
Some people will experience tingling all over or in a certain spot. Some people will experience apparently isolated spots of heat or cold. The best practice here is to attempt to get ahead of these phenomena. The Westerner not used to sitting in the Indian style position will soon begin to experience intense pain in the legs. There will come a time when the best strategy will be to sit and endure the pain until it has completely passed.