My Sister Is 53 And Has Twitching Of The Arm,

my sister is 53 and has twitching of the arm, shoulder and next for the past few years. She went to a neurologist 4 years ago and had testing and a MRI. They did not have a diagnosis. We are worried it might be something more. It has not affected her work and it comes and goes. She does not want to go to the doctors again due to the cost. We just want to make sure its not something more serious. but not sure what to do.