How to rearange the order of a list after an item was removed?

so, I have an endless runner and I create a new prefab when the player is a certain distance fromte last part. I have a list of these prefabs and the code chooses a random part every time it needs to spawn a new platform. I then add these spawned parts to a second list. In order to not run out of memory, I want to remove the first element in t$$anonymous$$s second list when the list has 10 elements in it. Is there a way to reorder the list so that all elements move down one place ? I will post my code under here, sorry if my explenation is not the best, ask my about it in the comments if you don't get somet$$anonymous$$ng. Thanks in advance.

using System.Collections.Generic; using Unity.Mathematics; using UnityEngine; using Random = UnityEngine.Random;

public class SpawnManager : MonoBehaviour { private const float PlayerDistanceSpawnLevelPart = 150f; private Vector3 lastEndPosition;

 [SerializeField] private Transform _levelPartStart;
 [SerializeField] private List<Transform> _partsList;
 [SerializeField] private Player player;
 [SerializeField] private List<Transform> _spawnedParts;
 
 void Awake()
 {
     lastEndPosition = _levelPartStart.Find("EndPosition").position;
 }

 

 void Update()
 {
     Vector3 playerPosition = player.transform.position;
     
     if (Vector3.Distance(playerPosition, lastEndPosition) < PlayerDistanceSpawnLevelPart)
     {
         SpawnLevelPart();
     }

     if (_spawnedParts.Count > 10)
     {
         _spawnedParts.Remove(_spawnedParts[0]);
         foreach (var part in _spawnedParts)
         {
             //here I would like to reorder the list so that the next time t$$anonymous$$s is called, I don't get a null 
             //reference exception
         }
     }
 }
 
 private void SpawnLevelPart()
 {
     Transform chosenLevelPart = _partsList[Random.Range(0, _partsList.Count)];
     Transform lastLevelPartTransform = SpawnLevelPart(chosenLevelPart,lastEndPosition);
     _spawnedParts.Add(chosenLevelPart);
     lastEndPosition = lastLevelPartTransform.Find("EndPosition").position;
 }

 private Transform SpawnLevelPart(Transform levelPart, Vector3 spawnPosition)
 {
     Transform levelPartTransform = Instantiate(levelPart, spawnPosition, quaternion.identity);
     return levelPartTransform;
 }
     

}