Gun Rotation Sway

Hi, I'm trying to have my weapon rotate with the mouse movements but then rotate back upright. And I want to limit it's rotation.

 using UnityEngine;
 using System.Collections;
 
 public class GunSway : MonoBehaviour {
     
 
     // Update is called once per frame
     void Update () 
     {
 
         if(Input.GetAxis("Mouse X")<0)
         print("Mouse Moved Left");
         if(Input.GetAxis("Mouse X")>0)
             print("Mouse Moved Right");
         if(Input.GetAxis("Mouse Y")<0)
             print("Mouse Moved Down");
         if(Input.GetAxis("Mouse Y")>0)
             print("Mouse Moved Up");
 
         if(Input.GetAxis("Mouse X")<0)
             transform.Rotate(0,1,0);
         if(Input.GetAxis("Mouse X")>0)
             transform.Rotate(0,-1,0);;
 
     }
 }