float startTime;
bool move;
Vector3 startPos;
Vector3 endPos;
float lengthMoving; // время за которое перемещаемся

void Start()
{
      startTime = Time.time;
      move = true;
      position = startPos;
}
void Update()
{
      if(move)
      {
         if((Time.time - startTime) == lengthMoving) move = false;
         position = Vector3.Lerp(startPos, endPos, (Time.time - startTime) / lengthMoving);
      }
}

Vector3 endPos;
float speed;

void Update()
{
         position = Vector3.Lerp(position, endPos, Time.deltaTime *speed);
}

using UnityEngine;

public class Temp : MonoBehaviour
{
    public int Compare(Transform x, Transform y)
    {
        float a_dist = Vector3.Distance(transform.position, x.position);
        float b_dist = Vector3.Distance(transform.position, y.position);
        return a_dist.CompareTo(b_dist);  
    }

    List<Transform> targets;
    Transform selectedTarget;  

    void Start()
    {
       targets = new List<Transform>();
       selectedTarget = null;
       AddAllEnemies();  
       targets.Sort(Compare);
    }
    //Остальное как у Вас
}