The latest addition to the YouTube music main screen is a carousel called 'Quick picks.' On first glance, it shows a bunch of songs you've likely listened to previously, but playing them actually starts a radio playlist full of similar sounds, so it's a great way to quickly start listening to a certain style of music without having to think too much.
You'll find 'Quick picks' on both desktop and mobile, where it appears to be rolling out widely today after previously being tested among a small number of users. I don't use YouTube Music a great deal (I'm a Spotify guy), so it's hard to say what method is used to select the tracks in the carousel. I've probably listened to all of those at some point, but it's not necessarily based on the recent plays.
The radio playlist is just what you'd expect, with a range of songs closely related to the starting track, seemingly from other artists I've also listened to rather than surfacing brand-new content. The carousel itself appeared quite far down my home screen but it may be pushed a little higher if it proves popular. Only four songs are displayed on mobile (more on desktop) but you can swipe to reveal even more options. If you just want to whack something on but don't have anything particular in mind, this is a convenient starting point.