Controller Rotation returns to Zero when there is no movement.

I have managed to get my character to face the direction he is moving in, however when the character is not moving, He faces his start position. All of the rotation values return to 0. Why does this happen?

Also how do I get my character to face the direction of my inputs in the air?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Playables;
 
 public class Aerial_Controler : MonoBehaviour {
 
     public CharacterController MyController;
     // Update is called once per frame
     public float GroundSpeed = 7f;
     public float CurrentSpeed;
     public float SprintSpeed = 10f;
     public float TimeZeroToMax = 2.5f;
     float accelRatePerSec;
     public float AerialSpeed = 2f;
     public float GravityStrength = 5f;
     public float JumpSpeed = 10f;
     public Transform CameraTransform; 
     bool canJump = false;
     float verticalVelocity;
     Vector3 velocity;
     Vector3 groundedVelocity;
     Vector3 normal;
     bool onWall = false;
 
     private void Start()
     {
         accelRatePerSec = SprintSpeed / TimeZeroToMax;
         CurrentSpeed = 0f;
         MyController = GetComponent<CharacterController>();
 
     }
 
 
 
     void Update()
     {
         bool run = Input.GetKey(KeyCode.M);
 
 
         if (run)
         {
             CurrentSpeed += accelRatePerSec * Time.deltaTime;
             CurrentSpeed = Mathf.Min(CurrentSpeed, SprintSpeed);
         }
 
         else
         {
             CurrentSpeed = GroundSpeed;
         }
 
         if (Input.GetKeyUp(KeyCode.M))
         {
             CurrentSpeed += accelRatePerSec * Time.deltaTime;
             CurrentSpeed = Mathf.Max(GroundSpeed, CurrentSpeed);
         }
 
         if (run && !MyController.isGrounded)
         {
             CurrentSpeed = GroundSpeed + AerialSpeed;
         }
 
         Physics.IgnoreLayerCollision(9, 10);
 
         Vector3 myVector = Vector3.zero;
 
         //get input from the player
         Vector3 input = Vector3.zero;
         input.x = Input.GetAxis("Horizontal");
         input.z = Input.GetAxis("Vertical");
         input = Vector3.ClampMagnitude(input, 1f);
         transform.rotation = Quaternion.LookRotation(groundedVelocity);
 
 
         if (MyController.isGrounded)
         {
             myVector = input;
             Quaternion inputRotation = Quaternion.LookRotation(Vector3.ProjectOnPlane(CameraTransform.forward, Vector3.up), Vector3.up);
             myVector = inputRotation * myVector; //rotate input by direction of the camera
             myVector *= CurrentSpeed;
         }
         else
         {
             Quaternion inputRotation = Quaternion.LookRotation(Vector3.ProjectOnPlane(CameraTransform.forward, Vector3.up), Vector3.up);
             input = inputRotation * input;
             myVector = groundedVelocity;
             myVector += input * AerialSpeed;
         }
 
         myVector = Vector3.ClampMagnitude(myVector, CurrentSpeed);
         myVector = myVector * Time.deltaTime;
 
 
         verticalVelocity = verticalVelocity - GravityStrength * Time.deltaTime;
         if (Input.GetButtonDown("Jump"))
         {
             if (onWall)
             {
                 Vector3 reflection = Vector3.Reflect(velocity, normal);
 
                 Vector3 projected = Vector3.ProjectOnPlane(reflection, Vector3.up);
                 groundedVelocity = projected.normalized * CurrentSpeed + normal * AerialSpeed;
             }
             //add Jumped to vertical velocity
             if (canJump)
                 verticalVelocity += JumpSpeed;
         }
         myVector.y = verticalVelocity * Time.deltaTime; //add new speed, to old speed, for acceleration
 
         //use input to move the character
         CollisionFlags flags = MyController.Move(myVector);
         velocity = myVector / Time.deltaTime;
         print(velocity);
         //use flags to determine if character can jump or not
         //if on ground
         //set canJump to true
         if ((flags & CollisionFlags.Below) != 0)
         {
             groundedVelocity = Vector3.ProjectOnPlane(velocity, Vector3.up);
             canJump = true;
             verticalVelocity = -3f;
             onWall = false;
         }
         else if ((flags & CollisionFlags.Sides) != 0)
         {
             canJump = true;
             onWall = true;
         }
         else
         {
             canJump = false;
             onWall = false;
         }
     }
 
     private void OnControllerColliderHit(ControllerColliderHit hit)
     {
         normal = hit.normal;
     }
  
 }