The twitching in your arm sounds like quite an unpleasant disruption to your life. As you have been reading, dystonia is a condition in which muscles (often in a single part of the body) will contract involuntarily and then cause a twisting in the affected body part. Some dystonias are inherited genetically, and these patients will often start having symptoms in childhood. In other patients, a dystonia may develop later in life. Notably, dystonia symptoms often get worse with a specific activity--for example a writer's cramp--and can also worsen with stress or fatigue. There are several classes of medications that have been used with good effect for many patients with dystonia. Surgical intervention is typically reserved for the most refractory cases.
In your situation, the best thing to do is to see your primary care physician
for a thorough history and exam. Your doctor
will want to find out more about your symptoms as well as any family history of similar complaints. In addition, an exam will be very important to determine if something else may be causing your muscle twitching. While dystonia is one cause of muscle twitching and contraction, many other medical conditions can also present this way. Your medical history and exam will be very important in helping to sort this out and determine if you need to see a specialist such as a neurologist