C# Twitchy Camera Movement

I have script that makes the main camera follow my mouse. However sometimes the main camera's movement can be very twitchy. I used Time.smoothDeltaTime instead of Time.deltaTime but there still seems to be a bit of twitchy movement from the Main camera. What else can I do to try to smooth out this erratic movement?

 using UnityEngine;
 using System.Collections;
 
 public class Camera_Move : MonoBehaviour {
     public float sensitivityX = 2F;
     public float sensitivityY = 2F;
     // Use this for initialization
     void Start () {
     
     }
 
     // Update is called once per frame
     void Update ()
     {
             float positionX = transform.position.x + Input.mousePosition.x * sensitivityX;
             float positionY = transform.position.y + Input.mousePosition.y * sensitivityY;
             
             transform.position = new Vector3( positionX, positionY, 0) * Time.smoothDeltaTime;
     }
 }