How do I stop my player or camera from jittering during player movement?

In my game, I have a third person character. The player moves with a rigidbody and has isKinematic set off with interpolate on. In the script, it moves with Rigidbody.MovePosition with the y position froze. Here's my player script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerController : MonoBehaviour
 {
    public float speed;
 
    public Rigidbody rb;
 
    public Transform camPos;
 
    // Start is called before the first frame update
    void Start()
    {
       rb = GetComponent<Rigidbody>();
       camPos = Camera.main.transform;
    }
 
    private void FixedUpdate()
    {
       if (Input.GetKey("w"))
       {
           rb.MovePosition(transform.position + (camPos.forward * speed * Time.fixedDeltaTime));
       }                                         
       if (Input.GetKey("s"))
       {
           rb.MovePosition(transform.position + (-camPos.forward * speed * Time.fixedDeltaTime));
       }
       if (Input.GetKey("d"))
       {
           rb.MovePosition(transform.position + (camPos.right * speed * Time.fixedDeltaTime));
       }
       if (Input.GetKey("a"))
       {
           rb.MovePosition(transform.position + (-camPos.right * speed * Time.fixedDeltaTime));
       }
 
       rb.velocity = Vector3.zero;
    }
 }

For my camera, I have it lookat the player and lag behind smoothly. Here's that script:

 //Hakeem Thomas
 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class CamPos : MonoBehaviour
 {
    public Transform target;
    public float smoothTime = 0.5F;
    private Vector3 velocity = Vector3.zero;
 
    public GameObject player;
 
    private float mouseX, mouseY;
    public int mouseX_Speed, mouseY_Speed;
    
    //mouseSensitivity
    public int turnSpeed;
 
    void getMouseXY()
    {
        mouseX += Input.GetAxis("Mouse X") * smoothTime;
        mouseY -= Input.GetAxis("Mouse Y") * smoothTime;
    }
    void LateUpdate()
    {
        getMouseXY();
        // Define a target position above and behind the target transform
        Vector3 targetPosition = target.TransformPoint(new Vector3(0, 1.5f, -2.5f));
 
        // Smoothly move the camera towards that target position
        transform.position = Vector3.SmoothDamp(transform.position, targetPosition, ref velocity, smoothTime);
        transform.LookAt(target);
 
        target.rotation = Quaternion.Euler((mouseY * mouseY_Speed), (mouseX * mouseX_Speed), 0);
        player.transform.rotation = Quaternion.Euler(0, (mouseX * turnSpeed), 0);
 
    }
 }

My issue is that whenever the player moves either the camera/player jitters. I have debugged the player transform y position to make sure it wasn't moving up or down(it doesn't). To help with this issue I have either turned down the Fixed Timestep under Time in the project settings or put the code in the camera script is fixed update instead of late update(which I have researched is an issue). I know MovePosition for the player isn't the right way to move, but I don't know how to make the player move in the direction the camera is facing with rb.velocity. I suspect the issue may lay in the player script with variable camPos. Either way, I would like to stop the jittering.