I have a laggy camera, how do i fix it

I have a problem with my camera. Since i linked it to the upper bosy rotating its just a little laggy, it doesnt fill so smooth as before. One extra question for some reason when i start unity the camera(upperBody) starts facing upwards probably beacuse of clamp but it shouldnt.Also I imported a soldier model from blender with bones, if that helps. I will be happy for any kind of help.

public class playerLook : MonoBehaviour
{
public float mouseSensitivity;

public Transform playerBody;
public Transform upperPlayerBody;

float xRotation;
// Start is called before the first frame update
void Start()
{
    Cursor.lockState = CursorLockMode.Locked;
}

// Update is called once per frame
void Update()
{
    float mouseX = Input.GetAxis("Mouse X") * mouseSensitivity * Time.deltaTime;
    float mouseY = Input.GetAxis("Mouse Y") * mouseSensitivity * Time.deltaTime;

    xRotation -= mouseY;
    xRotation = Mathf.Clamp(xRotation, 30f, 120f);
    upperPlayerBody.transform.localEulerAngles = new Vector3(xRotation, 0f, 0f);

    playerBody.Rotate(Vector3.up * mouseX);
    upperPlayerBody.Rotate(Vector3.right * mouseY);
}

}

I’m not sure if this is the problem, but you can try:

upperPlayerBody.transform.localRotation = Quaternion.Euler(xRotation, 0f, 0f);

on line 19.

It seems that StringAtlas has helped in which case please mark this question as answered, otherwise…
Rather than applying these movements in update, do it in LateUpdate.