How to make a platform start moving when the player steps on it

Here's the script I've tried so far

 using UnityEngine;
 using System.Collections;
 
 public class Moving_Platform_Script_2 : MonoBehaviour {
     public Transform position1;
     public Transform position2;
     public float speed= 15f;
     public bool Switch = false;
     public bool start=false;
     public GameObject player;
     public GameObject platform;
     
     
     void FixedUpdate(){
         if(start==true){
         // For these 2 if statements it's checking the position of the platform
         if(transform.position==position2.position){
             Switch=true;
         }
         
         if(transform.position==position1.position){
             Switch=false;
         }
         if(Switch){
             transform.position=Vector3.MoveTowards(transform.position, position1.position, speed*Time.deltaTime);
         }
         else{
             transform.position=Vector3.MoveTowards(transform.position, position2.position, speed*Time.deltaTime);
             
         }
         }
         
     }
     void OnCollisionStay(Collision player){
             if (Switch) {
             player.transform.position=Vector3.MoveTowards(transform.position, position1.position, speed*Time.deltaTime);
         }
         else {
             player.transform.position=Vector3.MoveTowards(transform.position, position2.position, speed*Time.deltaTime);
             
         }
     }
     void OnCollisionEnter (Collision player){
         if (start == false) {
             start = true;
         }
         }
 
 }

Any help would be appreciated