Help With Quaternion.LookRotation

I’m making a fairly basic 3D platformer, and trying to have my character look in the direction they are facing. When I try out the game with the line disabled, the script works fine (allows the character to move and jump). However, when I enable the line with Quaternion.LookDirection and try moving, the character rotates absurdly fast and cannot be controlled. I have a feeling I’m doing this wrong but can’t find anything on how exactly I’m supposed to be using it.

using UnityEngine;
using System.Collections;

public class Movement : MonoBehaviour {

	public float speed = 6.0F;
    public float jumpSpeed = 8.0F;
    public float gravity = 20.0F;
	private float overAllSpeed;
    private Vector3 moveDirection = Vector3.zero;
    void FixedUpdate() {
        CharacterController controller = GetComponent<CharacterController>();
        if (controller.isGrounded) {
            moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0.0f, Input.GetAxis("Vertical"));
            moveDirection = transform.TransformDirection(moveDirection);
            moveDirection *= speed;
            if (Input.GetButton("Jump"))	{
				moveDirection.y = jumpSpeed;
			}
        
        }
		else if(controller.isGrounded==false)	{
		moveDirection.x = Input.GetAxis("Horizontal");
		moveDirection.z = Input.GetAxis("Vertical");
        moveDirection = transform.TransformDirection(moveDirection);
        moveDirection.x *= speed;
		moveDirection.z *= speed;
		moveDirection.y -= gravity * Time.deltaTime;
		
		}
     
        controller.Move(moveDirection * Time.deltaTime);
		overAllSpeed=Mathf.Abs((moveDirection.x+moveDirection.z)/2);
		Debug.Log(overAllSpeed);
		if (overAllSpeed!=0)
			transform.rotation = Quaternion.LookRotation(moveDirection);
    }
}

Because you’re transforming the moveDirection vector into world coordinates I think you’d have better luck with Transform.LookAt instead. It takes a world position and orients the rotation towards that position.