Can't use AddRelativeForce properly

Unity Engine
1

I am trying to use rigidbody’s AddReletive force to make the movement in my game less stale as it is with just using transforn.Translate, but when I try to use it, it launches my character up as well as forwards.

private void FixedUpdate()
    {
        if (Input.GetKey(KeyCode.W))
        {
            if (IsRagDoll == false)
            {
                body.GetComponent<Rigidbody>().AddRelativeForce(0, 0, -8, ForceMode.Impulse);
            }
        }

the game object “body” is linked to my character that I am trying to move.
if you need to see more, let me know, and I can send it.

I can't get addrelativeforce to work
2

Relative means it takes the transform’s rotation into account.

3

yes, I need that so when the character turns around it will still move forwards, but it’s rotation is 0, 0, 0 so I don’t know why it is going up.

edit: it never rotates on the x axis, only the y