Space Shooter-How do I make a gameobject move and then stop?

I’m playing around with a space shooter tutorial I found on the unity website, and I’m trying to make a boss enemy that appears when I reach a certain amount of points. But I can’t figure out how to make the boss move to the center of the screen. I think it has something to do with the mover script I made for the other enemies. The other enemies move all the way to the bottom of the screen. How can I make a boss mover script that just has it move half way on the screen?

public class Mover : MonoBehaviour {
public float speed;
private Rigidbody rb;

void Start()
{
   rb = GetComponent<Rigidbody>();
   rb.velocity = transform.forward * speed;
}
}

The easiest solution would be to clamp the position in FixedUpdate().

void FixedUpdate()
{
   if(transform.position.y >= whatever point you want)
   {
      transform.position = new Vector3(transform.position.x, whatever point you want, transform.position.z);
   }
}

Not the ideal solution but will work just fine for you.

Depending on what your game does (or the boss, actually)… if it just stops when it reaches that ‘height’, you could set the velocity to zero, too.