Locking script not locking properly

The purpose of this script is to lock onto GameObjects with the tag of Targetable and to target the closest one.

Problems:
It only targets the one closest at the start of the scene rather than constantly checking.
It doesn't properly face the target rotating in weird ways.

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class Closestlock : MonoBehaviour {
5.     //Holds all GameObjects in the scene with the tag of Targetable.
6.     public GameObject [] targetable;
7.     //The closest GameObject
8.     public GameObject targeted;
9.     // Use this for initialization
10.     // Used to calculate which GameObject is closer.
11.     float minDist;
12.     public float dist = 0;
13.     // how quickly you want to be able to look at the target.
14.     public float speed;
15.     void Start () {
16.         //Fills the array with GameObjects
17.         //uncomment this line if you do not need to check if new objects are being instantiated
18.         //targetable = GameObject.FindWithTag("Targetable");
19.     }
20.    
21.     // Update is called once per frame
22.     void Update () {
23.            
24.         //Fills the array with GameObjects
25.         targetable = GameObject.FindGameObjectsWithTag("Targetable");
26.         //Runs through each GameObject
27.         foreach(GameObject target in targetable){
28.             //Stores the shortest distance and sets "targeted" to the shortest distance.
29.             dist = Vector3.Distance(transform.position, target.transform.position);
30.             //Checks to see which is closer.
31.             if(minDist == 0){
32.                 targeted = target;
33.                 minDist = dist;
34.                 }
35.             if(dist < minDist){
36.                 minDist = dist;
37.                 targeted = target;
38.             }
39.         }
40.         // lock on target
41.         Quaternion targetRotation = Quaternion.LookRotation(targeted.transform.position);  
42.         // Smoothly rotate towards the target point.
43.         transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speed * Time.deltaTime);
44.    
45.     }
46. }
47.  
48.  

 

I need it to smoothly move in between which as far as i know will snaps between rotations