Barbell squats?
I certainly don’t do it for anyone else, and although it’s better for waking up and getting my stuff together than for relaxing, it brings me into a state of mind that’s hard to attain otherwise. Others here would probably call it a spiritual experience.
But not me. It’s a release of adrenaline and other hormones, actually. A purely physical biochemical process.
And occasionally I go for a walk on an impulse, usually taking my homework reading material with me.
In the same vein, I’ve abused my student’s privilege of free public transport before to board a random bus and read my stuff in there, get off at a random stop, walk around a bit, and then take a bus back home again.
Furthermore I read books, watch films or series or comedians, and spend time on the internets in various ways (e.g. TV Tropes, creepypasta, Omegle or Fluther).