I have had muscle twitches and spasms for years although the emphasis was more on spasms and cramps for a long time. For a couple of years now I have been having increasing twitches. It was at night only for a while and now 24/7. It is rare that I am ever completely without twitches. There is no muscle weakness although when the twitches are really bad, my muscles feel tired. If you had all of the tests and they were negative, i.e. didn't prove anything more serious, and you still have intermittent twitches all over then I suspect it's possible that you have Benign Fasciculation Syndrome (BFS). Following is some information I found about the syndrome. I have about decided that I have BFS rather than RLS (Restless Legs).
What are the symptoms of BFS?
This condition represents a hyperexcitability of the neuromuscular system.
Common symptoms of BFS are frequent muscle twitches (fasciculations or fascics), generalized fatigue, "pins and needles" sensations, migrating numbness, muscle cramping and/or spasms in the affected areas (usually the feet and calves), muscle aches and stiffness exercise intolerance, headaches, and itchiness.
Clinically some patients have mild increases in creatine kinase. Muscle biopsy may show mild neurogenic changes. Electrodiagnostic studies show peripheral nerve hyperexcitability.
Often the symptoms will get worse at night, or during periods of sickness or viral infections, stress, or overexertion.
Many people experiencing these symptoms fear they may have ALS or MS. A simple clinical rule is that fasciculations in relaxed muscle are never indicative of motor system disease unless there is an associated weakness, atrophy, or reflex change. What are fasciculations?
Fasciculations, or fascics are localized twitches of the muscle fibers.
From the On-Line Medical Dictionary:
A small local contraction of muscles, visible through the skin, representing a spontaneous discharge of a number of fibres innervated by a single motor nerve filament.
Copy this web link into your browser and check out the description of Restless Legs Syndrome (RLS):
http://www.ninds.nih.gov/disorders/restless_legs/detail_restless_legs.htm