Google Search started to roll out the age verification that it said it would begin doing a couple of weeks ago. Yes, it is not just YouTube, it goes across Google Search ads too, as we Reddit user spotted this (hat tip to Tech Issues Today where Google Search posted a notice to ask the user to confirm they are an adult.
Here is that screenshot:
It reads:
Google changed some of your settings:
We changed some of your account settings because we couldn't confirm you're an adult. Check if your new settings are right for you.
You can learn more about these changes over here.
Forum discussion at Reddit.