<style>
    #loading-overlay {
        background-color: rgba(0,0,0,0.7);
        background-image: url(' ..... ') // add loading spinner here
        background-position: center;
        position: fixed;
    }
</style>

<div id="loading-overlay" style="display:none"></div>

<script>
jQuery( document ).ready(function() {
    jQuery('#question-submit-btn').click(function() {
        setTimeout(function (){
            var validationCheck = document.getElementsByClassName('validation-failed');
            if (validationCheck.length > 0) {
                validationPassed = false;
            } else if (validationCheck.length == 0) {
                validationPassed = true;
            }
            if ( validationPassed == true ) {
                jQuery('#loading-overlay').addClass('overlay-active');
            }
        },300);
    });
});
</script>