I have moaned about this before (here for example) ...but it's my back you see - well, actually it's not even my back. It seems to be the result of the sciatic nerve in my back causing trouble elsewhere - referred pain they call it ...in this case in my Tibialis anterior or more specifically the peroneal nerve.
If you have had lumbago you will know about shooting pains and this, whatever it is, is a cute variation on that. The only vague warning sign is a dull aching sensation just to the right of the bottom of my spine ...and then suddenly there is a flash and I am hopping around the room releasing a stream of invective containing a lot of 'f' words and no shortage of 'b' words. The feeling is as if some invisible presence has taken an invisible 6" nail and hammered it, with great force, right into the muscle at the top of my shin (Tibialis anterior); then this evil demon proceeds to heat the nail to excruciating temperatures ...and sometimes there is the added agony of something like a zappy electric charge being switched rapidly on and off at the point where the 'nail' has been hammered in. These attacks probably only last 20 seconds but they leave me in a sweaty heap afterwards.
That is normally the sign that I should have taken a painkiller half an hour before...