Quote Originally Posted by Hsing-ee View Post
If it was relieved by some stretching and twisting etc, probably there was some residual tension in the muscle fibres. This can happen if you are stressed or do a repetitive action for a long time. I noticed it when I was doing a lot of night driving when I was tired, ended up gripping the wheel when it only needed to be held securely. The tension remains after the action is over, like a kind of tetanus. Then when you need to do something with a slightly different deployment of muscle it causes trembling. The stretching and twisting relaxes the tense muscle fibres and re-sets them so you can use them in another way.

In terms of diet, potassium and calcium are necessary for good nerves and muscle control, so have a banana milk-shake for breakfast for a few days and see if that make a difference.
I have an orange, apple and banana every lunchtime. I normal go to shoot after walking the dog so it's probably not tension.
All the points you make are relevant, especially wheel gripping.