On the checkout page if you're purchasing a shippable product the Shipping is the same as billing address checkbox is checked by default. If you would like this checkbox to be unchecked by default then you can insert the following code at the top of your checkout page:

<script>
jQuery(function() {
jQuery('#mm_checkbox_billing_equals_shipping').prop('checked', false);
mmjs.toggleShippingInfo();
});
</script>