try and use WP_Query() and reset the query at the end;
example:
<?php $cat_query = new WP_Query('cat=16&posts_per_page=3'); ?>
<?php while ($cat_query->have_posts()) : $cat_query->the_post(); ?>
<ul>
<li>
<?php the_title(); ?>
<?php the_content(); ?>
</li>
</ul>
<?php endwhile; wp_reset_postdata(); ?>
if this does not work, you might need to post a link to your site to illustrate the output of your code.
You may also want to use in-built recent posts widget from the default Jetpack Plugin.
It can be customized to fit needs.
–I have read somewhere that using executable php on pages – compromises security.–