This could be an experiment. Google often performs A/B tests of different layouts on various of its search pages while working on new features. Usually there's a link to give feedback when they show you something you don't like. I suggest submitting that feedback.

Whether you can then disable the experiment is hard to say. Sometimes clearing your Google cookies will get you out of the group (this will log you out). While viewing a page on the site, click the lock icon at the left end of the address bar. After a moment, a "Clear Cookies and Site Data" button should appear at the bottom. Go ahead and click that. Firefox will ask you to confirm; go ahead and confirm.

Then try reloading the page. Does that help? Does it stay normal after logging into your account?

Thank you for your response -- the 'tiles' disappeared when I cleared the cookies as you suggested, but appeared again when I logged back into my account. There was no feedback link present on the page, but I sent feedback through the settings menu. We'll see.... I appreciate your answer as it at least prompted me to send feedback!