My Space Shooter ship fires a single shot immediately after starting the game, without ANY input at all...

My script's coding is identical to both the tutorial's script's coding (BESIDES THE OBVIOUS DIFFERENCE BETWEEN 'rigidbody' AND 'GetComponent RigidBody ()') and the "Done" script that came with the project package. I have no idea what is going wrong. I will supply my script followed by the tutorial script and then the Done script. By t$$anonymous$$s point, the game should work properly, without immediately, prematurely firing a bolt.

Does anyone have an idea as to why t$$anonymous$$s might be happening? If I were to give a wild guess, it may have to do with nextFire, but I'm not at all sure.

MY SCRIPT CODING:

PlayerController:

... (skipped irrelevant coding)

 public GameObject shot;
 public Transform shotSpawn;
 public float fireRate;
 
 private float nextFire;

 void Update ()
 {
     if (Input.GetButton("Fire1") && Time.time > nextFire) 
     {
         nextFire = Time.time + fireRate;
         Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
     }
 }

 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
     GetComponent<Rigidbody>().velocity = movement * speed;

     GetComponent<Rigidbody> ().position = new Vector3 
     (
         Mathf.Clamp (GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax), 
         0.0f, 
         Mathf.Clamp (GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
     );

     GetComponent<Rigidbody> ().rotation = Quaternion.Euler (0.0f, 0.0f, GetComponent<Rigidbody> ().velocity.x * -tilt);
 }

}

THE TUTURIAL'S SCRIPT CODING:

PlayerController:

...

 public GameObject shot;
 public Transform shotSpawn;
 public float fireRate;

 private float nextFire;

 void Update ()
 {
     if (Input.GetButton("Fire1") && Time.time > nextFire)
     {
         nextFire = Time.time + fireRate;
         Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
     }
 }

 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
     rigidbody.velocity = movement * speed;

     rigidbody.position = new Vector3 
     (
         Mathf.Clamp (rigidbody.position.x, boundary.xMin, boundary.xMax), 
         0.0f, 
         Mathf.Clamp (rigidbody.position.z, boundary.zMin, boundary.zMax)
     );

     rigidbody.rotation = Quaternion.Euler (0.0f, 0.0f, rigidbody.velocity.x * -tilt);
 }

}

THE "DONE" SCRIPT CODING:

PlayerController:

...

 public GameObject shot;
 public Transform shotSpawn;
 public float fireRate;
  
 private float nextFire;
 
 void Update ()
 {
     if (Input.GetButton("Fire1") && Time.time > nextFire) 
     {
         nextFire = Time.time + fireRate;
         Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
     }
 }

 void FixedUpdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
     GetComponent<Rigidbody>().velocity = movement * speed;
     
     GetComponent<Rigidbody>().position = new Vector3
     (
         Mathf.Clamp (GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax), 
         0.0f, 
         Mathf.Clamp (GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
     );
     
     GetComponent<Rigidbody>().rotation = Quaternion.Euler (0.0f, 0.0f, GetComponent<Rigidbody>().velocity.x * -tilt);
 }

}