Why does my character eventually slow down and stop moving with MoveTowards()?

This is a turn based game I am testing from Unity. When I run it its fine in turn 1, in turn 2 it slows down and by turn 3 the character just stops moving. Apologies if this is an obvious issue but I would like to find a solution. I have already tried using FixedUpdate as well. I use MoveTowards in a while loop to move the character object.

Update()
{
    if (turn == true)
    {
        Move();
    }
}

Move() 
{

    pos = target.transform.position;
    StartCoroutine(MoveOverTime());

    IEnumerator MoveOverTime() 
    {
        while ((transform.position - pos).magnitude > 0.1f)
        {
            transform.position = Vector3.MoveTowards(transform.position, pos, 0.3f * Time.deltaTime);
            yield return null;
        }
        yield return null;
    }
    turn = false;
}