after exiting the car and re entering it I wont go forward

just wondering if anybody has had this issue I've made my own enter exit script using unity's car controller as a base car it seems to work fine but every now and then I will hop back in the car and it wont go forwards unless I reverse first?!? this has been bothering me because i wan to polish my car mechanics help much appreciated cheers!!

public class enterExit : MonoBehaviour {

 private bool inVehicle = false;
 public GameObject CarCam;
 public GameObject trigger;
 public GameObject car;
 public GameObject Player;
 public GameObject guiObj;
 public GameObject ExitPoint;

 void Start()
 {
     
 }

 void OnTriggerStay(Collider other)

 {
     if (other.gameObject.tag == "Player" && inVehicle == false) 
     {

         guiObj.SetActive(true);

         if (Input.GetKey(KeyCode.E))
         {

             inVehicle = true;
             Player.SetActive(false);
             car.GetComponent<Rigidbody>().isKinematic = false;
             CarCam.SetActive(true);
             car.GetComponent<CarUserControl>().enabled = true;
             car.GetComponent<CarController>().enabled = true;
             
             //car.GetComponent<CarAudio>().enabled = true;

         }  
     }
 }

 void OnTriggerExit(Collider other)

 {
     guiObj.SetActive(false);

 }

         void Update()
 {


     if (inVehicle == true && Input.GetKey(KeyCode.F))
     {
       
         Player.gameObject.transform.position = ExitPoint.transform.position;
         Player.SetActive(true);
         // check if grounded first 
         car.GetComponent<Rigidbody>().isKinematic = true;
         car.GetComponent<CarUserControl>().enabled = false;
         car.GetComponent<CarController>().enabled = false;
         CarCam.SetActive(false);
         //car.GetComponent<CarAudio>().enabled = false;
         inVehicle = false;
     }


     if (inVehicle == true)
     {

         guiObj.SetActive(false);

     }


 }

   
 

}