It would be great if you can confirm that the slowness is occuring even on pages without the ecommerce store functionality (e.g. About Us, Contact Us, FAQ page, etc). This will help narrow down the problem.
Are you able to determine if there are any Javascript errors on the page? You can open up the developer tool (F12) on your Chrome or Edge browser. Look for the Console tab and check for any reported errors after you refresh the page. Javascript errors can slow down the page.