Queue w Unity C#

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Car : MonoBehaviour
{
    public float MaxSpeed { get; private set; }
    public float Speed { get; set; }

    Rigidbody2D rb;

    private void Awake()
    {
        rb = GetComponent<Rigidbody2D>();
    }
    void Start()
    {
        MaxSpeed = 5;
        Speed = MaxSpeed;
    }

    void FixedUpdate()
    {
        rb.velocity = transform.right * Speed;
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Shop : MonoBehaviour
{
    Queue<Car> carsQueue = new Queue<Car>();
    Car activeCar;
    bool isShopEmpty = true;

    private void OnTriggerEnter2D(Collider2D collision)
    {
        Car car = collision.GetComponent<Car>();
        carsQueue.Enqueue(car);
        car.Speed = 0f;
    }

    private void OnTriggerExit2D(Collider2D collision)
    {
        activeCar.Speed = activeCar.MaxSpeed;
        isShopEmpty = true;
    }

    void Update()
    {
        if (!isShopEmpty) return;
        if (carsQueue.Count == 0) return;
        activeCar = carsQueue.Dequeue();
        isShopEmpty = false;
        activeCar.Speed = 1f;
    }

}