This occassionally pops up when I load site on mobile

That is being injected by a bad advertisement. (e.g. through an advertising network you have setup to display ads on your site)

This happened to us a few months ago. It was really bad. The best way I can suggest for how to determine where it's coming from is set up a test page with any advertising on it. Check to make sure you're getting the redirects on that page. Then systematically disable certain ads and see if the redirects still happen. When you disable something give it a while to make sure the redirects still happen or don't happen. There were times I'd disable something, the redirects would stop for a while, I would think I found the culprit, but then the redirects would start back. They're really tricky.

You can see my community post here: https://community.townnews.com/communities/1/topics/928-anyone-else-getting-spam-redirects-on-mobile-devices

If you're getting these in the Facebook app you need to clear your Facebook cache. That's the only place we see those on our website these days but I think that's a Facebook thing.