On some playlists (the last one this happened on was "Deep House Relax") when one song ends it starts the next some somewhere in the middle after an unusually long crossfade.
After some investigation, it seems this is a feature that some playlists have. This behavior should have a setting to disable it as it's quite disruptive to the listening experience in my opinion. (and apparently, also everybody else who joined in on this thread)
Important: This is not the regular crossfade! This starts songs literally a minute in, not just 12 seconds like the normal crossfade. This behavior seems to appear even with crossfade turned off!
macOS 10.13.6 (latest at the time)