how to play gif whenever button is clicked in javascript modal

i have a modal in javascript, when user clicks the modal button, the modal opens with a gif:

var modal = document.getElementById("myModals");


var btn = document.getElementById("myBtns");


var span = document.getElementsByClassName("closes")[0];

btn.onclick = function() {
  modal.style.display = "block";

}


span.onclick = function() {
  modal.style.display = "none";
}

modal.onclick = function() {
  modal.style.display = "none";
}


window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}

<a href="#" id="myBtns"></a>

<div id="myModals" class="modals">

  <!-- Modal content -->
  <div class="modal-contents">
    <img src="sample.gif" style="margin-top:-25%;margin-left:20%;width:60%">
    <span class="closes">&times;</span>
  </div>

</div>

so the issue here is the gif is played the first time, when user closes it and clicks button again the gif is displayed as it is without playing, can anyone please tell me what is wrong in here, thanks in advance