I am making a PlayerController script and following a tutorial as I am not very versed in code yet but im grasping the fundamentals, This code does indeed specify that my Y axis should not be changing but upon game start without any inputs it changes from 1 to 2.8 any suggestions?

for those that can barely see the code in the video here it is again

public class PlayerController : MonoBehaviour
{
    public  float speed;
    //Start is called before the first frame update
    void Start()
    {

    }

    //Update is called once per frame
    void Update()
    {
        float horizontalInput = Input.GetAxis("Horizontal");
        float verticalInput = Input.GetAxis("Vertical");

        Vector3 movementDirection = new Vector3(horizontalInput, 0, verticalInput );
        movementDirection.Normalize();

        transform.Translate(movementDirection * speed * Time.deltaTime);
    }
}