404 Page on the website is getting too many sessions

I was advised by ChannelAdvisor that I should open a case with Shopify, as this issue is not related to the ChannelAdvisor integration.
We run a lot of Google catalog ads. Seeking a possible correlation between our 404s and Google catalog ads? We mainly get 404s when someone goes to a link of an out of stock product page, or a product that was recently added to a separate parent listing…
Will someone please advise as to why this 404 Page on the website is getting so many sessions? Thanks!