rotate strange moving position unity code example

Example: unity smoothly rotate

private float desiredRot;     public float rotSpeed = 250;     public float damping = 10;      private void OnEnable() {         desiredRot = transform.eulerAngles.z;     }      private void Update() {         if (Input.GetMouseButton(0)) {              if (Input.mousePosition.x > Screen.width / 2) desiredRot -= rotSpeed * Time.deltaTime;              else desiredRot += rotSpeed * Time.deltaTime;          }          var desiredRotQ = Quaternion.Euler(transform.eulerAngles.x, transform.eulerAngles.y, desiredRot);         transform.rotation = Quaternion.Lerp(transform.rotation, desiredRotQ, Time.deltaTime * damping);     }