Search Commerce Products by Tags
This should work (set the limit to whatever you want/need):

{% set tag = craft.tags.title(tagTitle).first() %}    

{% paginate craft.commerce.products.relatedTo(tag).limit(10) as pageInfo, products %}

    {% for product in products %}

        {{ product.title }} etc

    {% endfor %}

    {% if pageInfo.prevUrl %}&lt;a href="{{ pageInfo.prevUrl }}"&gt;Previous Page&lt;/a&gt;{% endif %}
    {% if pageInfo.nextUrl %}&lt;a href="{{ pageInfo.nextUrl }}"&gt;Next Page&lt;/a&gt;{% endif %}


For more on the pagination side of things, see: https://craftcms.com/docs/templating/paginate