It's not just you, and it's not just your imagination. YouTube is reportedly experiencing video playback issues around the world, and the problems with playback also affect YouTube TV and Google TV.
They are working on a fix.
Jay Peters / The Verge:
The issue appears to affect other services that use the YouTube infrastructure too, including YouTube TV and the movies and TV shows you'd purchase through Google TV (formerly known as Google Play Movies & TV). We couldn't load them.
In our initial testing, the YouTube website seemed to load just fine, but videos themselves would continuously show the loading wheel. One Verge staffer got a video to load after about a minute. As of about 8:00PM ET, though, we see error screens like this whenever we try to watch a video: