This is as good as my answer can get until the question gets more specific:
(function blink() {
$('.demo').fadeOut(Math.random()*500).fadeIn(Math.random()*400, blink);
})();
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<span class="demo">I'm blinking!</span>
4
solved How to add randomness to the blink effect? [closed]