SO - 21312218

HTML

<div class="wrap">
    <input id="test-1" type="radio" name="testing" checked />
    <input id="test-2" type="radio" name="testing" />
    <input id="test-3" type="radio" name="testing" />
</div>
<button id="start-stop">Start/stop</button>

JavaScript

jQuery(function () {
   var toggle = null;
    $("#start-stop").click(function () {
    	if(toggle == null) {
    		toggle = false;
	        setInterval(function () {
	            if(toggle)
	           		$('.wrap input').eq(($('input:checked').index() + 1) % 3).prop('checked', true);
	          }, 1000);
        }   
        toggle = !toggle;
    }); 
});