How Return Or Restart A Coroutine When A Variable Increase?

Hi, I have 2 scripts one for spawn second for object collision. I want when every time object collision happen level int increase and every time level int increase my coroutine restart

 public class LevelManager : MonoBehaviour
 {
     public static LevelManager Instance;
     public int Stage = 1;
 
     void Start()
     {
         StartCoroutine(StartTime());
     }
     void Update()
     {
         Levels();
     }
 void Levels()
     {
         switch (Stage)
         {
         case 5:
             CannonSpeed = 24f;
             break;
         case 4:
             CannonSpeed = 12f;
             break;
         case 3:
             CannonSpeed = 6f;
             break;
         case 2:
             CannonSpeed = 3f;
             break;
         case 1:
             CannonSpeed = 1.5f;
             break;
         }
     }
 public IEnumerator StartStage() 
     {
         GameObject Bullet = PoolManager.Instance.GetPooledObject();
         Bullet.transform.position = Cannon.transform.position;
         Bullet.transform.rotation = Cannon.transform.rotation;
         Bullet.SetActive(true);
         yield return null;
     }
     public IEnumerator StartTime() 
     {
         yield return new WaitForSeconds(Delay);
         StartCoroutine(StartStage());
     }
 
 //Second Script
 public class Bullet : MonoBehaviour
 {
    
     void OnTriggerEnter(Collider hit)
     {
         if(hit.gameObject.tag == "Target")
         {
             gameObject.SetActive(false);
             gameObject.GetComponent<Rigidbody>().velocity = Vector3.zero;
             LevelManager.Instance.Stage++;
         }else if(hit.gameObject.tag == "Death")
         {
             gameObject.SetActive(false);
             gameObject.GetComponent<Rigidbody>().velocity = Vector3.zero;
             LevelManager.Instance.GameOver();
         }
     }
 
 
 }