try to rotate a character controller when translating on z only

Hi Guys

I am trying to learn scripting in unity, and I am having a really hard time to get my character controller working.

I would like the rotate my character controller when translating on z only

My character prefab currently have

• character controller

• movement script i put together

  using UnityEngine; using System.Collections;

  public class movement : MonoBehaviour {

     public float speed = 350.0F;
       public float jumpSpeed = 300.0F;
       public float gravity = 500.0F;
       private Vector3 moveDirection = Vector3.zero;
   
   
       void FixedUpdate() {
           CharacterController controller = GetComponent<CharacterController>();
           if (controller.isGrounded) {
               moveDirection = new Vector3(Input.GetAxis("Vertical")*-1, 0, Input.GetAxis("Horizontal"));
               moveDirection = transform.TransformDirection(moveDirection);
               moveDirection *= speed;
               if (Input.GetButton("Jump"))
                   moveDirection.y = jumpSpeed;
   
   
                     }
       
           moveDirection.y -= gravity * Time.deltaTime;
           controller.Move(moveDirection * Time.deltaTime);
   
   
   
       
       
   
           Quaternion rot = new Quaternion();
           rot.SetLookRotation(moveDirection);
           transform.rotation = rot;
               }
   
   
   
       }
   
  

Right now the character just turning in all kinds of weird direction

Can someone please let me know where I did wrong

Thanks