Unity FPS camera z axis rotating problem

public float xMoveThreshold = 1000.0f;
public float yMoveThreshold = 1000.0f;

public float yMaxLimit = 45.0f;
public float yMinLimit = -45.0f;


float yRotCounter = 0.0f;
float xRotCounter = 0.0f;


// Update is called once per frame
void Update()
{
    xRotCounter += Input.GetAxis("Mouse X") * xMoveThreshold * Time.deltaTime;
    yRotCounter += Input.GetAxis("Mouse Y") * yMoveThreshold * Time.deltaTime;
    yRotCounter = Mathf.Clamp(yRotCounter, yMinLimit, yMaxLimit);
    transform.localEulerAngles = new Vector3(-yRotCounter, xRotCounter, 0);
}