I have got a problem with Player! The player shakes. What is the problem? How to fix?

 public Vector3 curPosition;
 public Vector3 nextPosition;
 Rigidbody playerRigidbody;
 float camRayLength = 100f;
 public float speed;
 public bool isMove = false;
 int floorMask;
 void Awake(){
     floorMask = LayerMask.GetMask ("Floor");
     playerRigidbody = GetComponent <Rigidbody> ();
 }
 void Start(){
     isMove = false;
     curPosition = transform.position;
     nextPosition = transform.position;
 }
 void Update(){
     if (Input.GetMouseButtonDown(0)){
         isMove = true;
         RaycastHit hit;
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
         if (Physics.Raycast (ray, out hit)) {
             nextPosition = hit.point;
         }
     }
     if (curPosition != nextPosition && isMove) {
         transform.position = Vector3.MoveTowards (transform.position, nextPosition, Time.deltaTime * speed);
         if (transform.position == nextPosition) {
             isMove = false;
         }
     }
 }
 void Turning (){
     Ray camRay = Camera.main.ScreenPointToRay (Input.mousePosition);
     RaycastHit floorHit;
     if(Physics.Raycast (camRay, out floorHit, camRayLength, floorMask)){
         Vector3 playerToMouse = floorHit.point - transform.position;
         playerToMouse.y = 0f;
         Quaternion newRotation = Quaternion.LookRotation (playerToMouse);
         playerRigidbody.MoveRotation (newRotation);
     }
 }
 void FixedUpdate (){
     Turning ();
 }![alt text][1]

[1]: /storage/temp/97391-player.jpg