That’s completely normal; the sensations are caused by some energy you’ve stored inside of you being re-activated. If you can follow those sensations to the root, the thorn, and then gradually work at that thorn, you can do some serious mental cleansing. If you’re able to remove all of the thorns, you will experience this zen-like peace for anything and everything that comes your direction.
This Michael Singer guy did a whole bunch of that kind of introspection, figured it all out, then wrote three different books on the process.