move enemy to random transform array

Ok you have two main problems going on. Your update loop and your translate function. The update loop runs every frame. You are starting a coroutine every frame. That coroutine loops infinitley while you are playing the game. So you are getting an infinite amount of inifite looping code. That will get you some crazy results. Instead you should be starting that coroutine on Awake or Start. Secondly it looks like your translate function is not used properly. You find newTree's position. but then you multiply that position by speed and Time.deltaTime. So you are going to move the object a tiny bit every 2 seconds and not to the actual found position. I suggest doing transform.position = newTree.position. That would instantly teleport the object to the found location. If you get that working then you can figure out how you want to move the object over time instead. Here is what I think you are trying to do in code. I haven't run it so it may have some typos:

 using System.Collections;
 using UnityEngine;
 
 public class MischiefMonkey : MonoBehaviour {
 
      [SerializeField]
     private float _speed = 7f;
     private float _closeThreshold = .1f;
     [SerializeField]
      private Transform[] _treeTopLocations;
 
     //The position we want to move to
     private Vector3 _targetPos;
      
     void Awake() {
         //Set our first target location to where we already are
         _targetPos = transform.position;
         //Startup your looping code that finds the target location every few seconds
         StartCoroutine(MonkeyMovement());
     }
 
      void Update()
      {
         //If we aren't close to our target location
         if(Vector3.Distance(transform.position, _targetPos) > _closeThreshold)){
             //Find the direction from where we are to where we want to be
             //Normalize it to get a direction rather than the whole distance
             Vector3_currentDir = (_targetPos - transform.position).normalized;
             //Move towards the target
             transform.Translate(_currentDir * _speed * Time.deltaTime);
         }
      }
 
      IEnumerator MonkeyMovement()
      {
          while (GameManager.gameManager.gameOver == false)
          {
              if (UIManager.uIManager.pauseMenuVisible == true)
              {
                  yield return null;
              }
              else
              {
                 //Dont get a new target for 2 seconds
                  yield return new WaitForSeconds(2);
                 //Get a new target
                 Transform newTree = TreeTopLocations();
                 _targetPos = newTree.position;
              }
          }
      }
 
      public Transform TreeTopLocations()
      {
          int randomIndex = Random.Range(0, _treeTopLocations.Length);
          return _treeTopLocations[randomIndex];
      }
 }