Started a couple of weeks ago. I noticed a mild weird sensation going down my left arm, then noticed that it was triggered by a certain movement of the head, bending forwards, everytime I did it, the shock was repeated. Some days later, it started going down the left side of my back, and then down the leg, till the knee, at the left side of the left leg. It is very quick. Most of all it is felt at the side of the back. Kind of like vibration. Any idea what this could be?
If it makes any difference, I am in my 20s.