Ok,so I do some of my learning stuff and I need my elevators to stop for a few secs

   private IEnumerator ReversePlatform()
    {
        yield return new WaitForSeconds(2); 
        _AccuTime = 0;
        speed = -speed;
    }

I call it here and my elevators just start to shake and go up, they wont go down

        if (_AccuTime > _RunTime)
        {
            StartCoroutine("ReversePlatform");
        }
        else 
        {
            transform.Translate(0, speed * Time.deltaTime, 0);
        }

I need them to go up, stay there like 2 secs and then go down continuously