Hi,
You might want to try taking some calcium and magnesium, calcium for the bones and magnesium for your muscles, and nerves. When we get older our need for calcium and magnesium increases, what we got from food or supplements when we were younger is now not enough. When I was in my thirty's I took 500/250 cal/mag, then I needed to go up to 1000/500 cal/mag, now I am at 1000/1000 cal/mag. and barely holding my own. I also take vitamn D because it helps the body utilize the cal/mag.
A lack of magnesium can play havoc with your whole system, it can cause insomnia, heart palpitations, coldness, internal shakes, tight hamstrings and muscles, muscle contractions in feet, legs, fingers, arms etc. and if low enough seizures, and outer shaking just to name a few.
Bell.