From my experience, we've haven't had this particular issue with our store too often, only very occasionally.
You might check the Shopify Status page and see if there are any issues that appear there. i don't see any that are showing on the overall system, but you can also log in at that page to see if there is anything showing specifically to your site.
There was a contact us link at the bottom of the status page you were just on.
Here is another link to it.
It will ask you to log in, then it will take you a page to enter a question. Enter anything in the question field and click Search, then there will be a button at the bottom to go to the page with chat/email support.