Hi,
So lately I've been getting a large dose of involuntary body movements/(kriya?).
It started a few weeks back perhaps 30 minutes into a sitting like a with a strong movement like a wave through the chest/upper body. Continuing on it kept coming up earlier and earlier while sitting. Yesterday it started up on its own while just laying on the couch and ended with a massive sobbing session. While sitting today I literally bounced off my bench several times until I finally just lay on the floor instead and let the thing run its course. After perhaps 30 minutes things started to calm down somewhat.
The shaking is quite intense, I had the thought today that I would probably be a big hit at a break dance competition.

Upper body, lower body, hips etc. all take turns shaking/moving, up/down/back/forward, all types.
Paying close attention, I've noticed that, while keeping attention focused on an object, after perhaps 10 seconds there is a pressure/movement/tension "forward" in the head, which, if I let it run its course, results in the movements starting up. I also have to be quite relaxed in the body, to much tension keeps anything from happening.
At this point, the movements pretty much go on continually unless I actively stop them, which is not hard to do with a little tension/resistance.
I read up on the phenomenon in Jack Cornfields "A path with heart", where he recommends keeping up just enough resistance to prevent the movements from happening so the energy can do something constructive instead of being "wasted" in movement. However, I must say that a felt quite good after my 40 minute shaking session today (I hesitate to call it meditation).
If I were to speculate, it almost feels like my body is trying to shake out years of accumulated body tension, but I really have no idea if that's close to the mark. I've been dealing with a lot of body tension for many years, which may or may not be relevant.
Anyway, any tips, ideas or comments are welcome. My plan is currently to simply let this have its course and see what happens. It's not unpleasant, and trying to resist it while meditating seems to be really bad for my concentration, so that doesn't seem to be a constructive option for me.
Thanks,
Simon