如何让这个图片的滑块拼图在没有按下按钮的情况下开始洗牌？

<div id="puzzle-container">
  <!-- 拼图小块 -->
  <div class="puzzle-piece"></div>
  <div class="puzzle-piece"></div>
  <!-- 更多拼图小块... -->
</div>

#puzzle-container {
  width: 400px;
  height: 400px;
  display: flex;
  flex-wrap: wrap;
}

.puzzle-piece {
  width: 100px;
  height: 100px;
  background-image: url('path/to/image.jpg');
  background-size: 400px 400px;
  background-position: 0 0;
  background-repeat: no-repeat;
}

function shufflePuzzle() {
  var puzzleContainer = document.getElementById('puzzle-container');
  var puzzlePieces = Array.from(puzzleContainer.getElementsByClassName('puzzle-piece'));

  // 洗牌算法
  for (var i = puzzlePieces.length - 1; i > 0; i--) {
    var j = Math.floor(Math.random() * (i + 1));
    var temp = puzzlePieces[i].style.backgroundPosition;
    puzzlePieces[i].style.backgroundPosition = puzzlePieces[j].style.backgroundPosition;
    puzzlePieces[j].style.backgroundPosition = temp;
  }
}

// 页面加载完成后自动洗牌
window.onload = function() {
  shufflePuzzle();
};