Help with this script? Keeps moving my objects around in run-time?

The purpose of t$$anonymous$$s script is when attached to a game object it creates a hovering effect. The only issue is that when play button is $$anonymous$$t and the game is running the object that have t$$anonymous$$s script move to different locations. They dont seem to stay in the location I've put them in during edit. What could be causing t$$anonymous$$s?

  public class hoveringeffect : MonoBehaviour {
  //public float horizontalSpeed;
   public float verticalSpeed;
   public float amplitude;

 public Vector3 tempPosition;
 void Start () {
     tempPosition = transform.position;
 }
 
 // Update is called once per frame
 void Update () {
     //tempPosition.x += horizontalSpeed;
     tempPosition.y = Mathf.Sin(Time.realtimeSinceStartup * verticalSpeed) * amplitude;
     transform.position = tempPosition;
 }
 }