Edit in JSFiddle

var checkbox = document.querySelectorAll("[type=checkbox]"),
    total = checkbox.length,
    actual = 0,
    fn = function(){
        checkbox[actual].checked = false;
        actual = actual == total - 1 ? 0 : ++actual;
        checkbox[actual].checked = true;
    };
checkbox[actual].checked = true;
setInterval(fn, 3000);

<input type = "checkbox" />
<input type = "checkbox" />
<input type = "checkbox" />