Stress, from high tension activities like swimming or hiking. Stretching before activities will virtually always prevent such symptoms from arising. You may also be suffering from malnutrition. Contact your local physician for more information.
It could be due to carpal tunnel which happens when you overuse a certain joint or muscle. If you do alot of computer work or repetitive tasks then this is likely the cause. It is very painful and right now there arnet a whole lot of things that can be done for it.
