The Cobiro app for Shopify will allow you to automatically have a product feed and a continuously updated Google Shopping campaign based on your catalog of products in your Shopify store.
To find the Cobiro app simply go to the Shopify App Store and search for Cobiro.
Click "Get" to begin the setup.
Select "New" to register a new email address with Cobiro, or "Existing" to add your Prestashop store to an existing Cobiro user.
Cobiro will automatically begin to import your product catalog.
Once you have filled in all the required fields to generate your Google Shopping campaigns, the Google Merchant Center and Google Shopping campaigns will be generated.