Player Movement, Enemy Movement, follow camera not disabled before pressing space

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using UnityEngine.SceneManagement;


public class GameState : MonoBehaviour {

    private bool gameStarted = false;

    [SerializeField]
    private Text gameStateText;

    [SerializeField]
    private GameObject player;

    [SerializeField]
    private BirdMovement birdMovement;

    [SerializeField]
    private FollowCamera followCamera;

    private float restartDelay = 3f;
    private float restartTimer;
    private PlayerMovement playerMovement;
    private PlayerHealth playerHealth;

    // Use this for initialization
    void Start () {
        Cursor.visible = false;

        playerMovement = playerMovement.GetComponent<PlayerMovement>();
        playerHealth = playerHealth.GetComponent<PlayerHealth>();

        //prevent player, bird from moving at beginning
        playerMovement.enabled = false;
        birdMovement.enabled = false;

        //prevent follow camera from moving
        followCamera.enabled = false;

    }


    private void StartGame() {
        //set game state
        gameStarted = true;
        //remove start text
        gameStateText.color = Color.clear;

        //enable player, bird movement
        playerMovement.enabled = true;
        birdMovement.enabled = true;

        //enable camera movement
        followCamera.enabled = true;

    }

    private void EndGame() {
        //set game state
        gameStarted = false;

        //re-enable text, change to 'game over'
        gameStateText.color = Color.white;
        gameStateText.text = "Game Over";

        //remove player from game
        player.SetActive (false);
    }

    // Update is called once per frame
    void Update () {

        //if game is not started, and player presses spacebar, then...

        //Input is a built-in class

        if(gameStarted == false && Input.GetKeyUp(KeyCode.Space)) {
            //start the game
            StartGame();
        }

        //if player is no longer alive...
        if(playerHealth.playerAlive == false) {
            //...end the game
            EndGame();

            //after game ends, start timer to count to restart
            restartTimer = restartTimer + Time.deltaTime;

            if(restartTimer > restartDelay){
                //reload the current level
                SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex); 
            }
        }
    }
}

playerMovement = playerMovement.GetComponent<PlayerMovement>();