Taking 1mg klonopin, (clonazepam) .5am & .5pm. getting trembling shaking feeling internally. is this a side effect of withdrawl or breakthrough anxiety?

Depends: If you get the Anxiety between 9-12 hours after the first dose that would be more likely. Typically break through is not seen as much in my experience when the twice daily doses are 8-10 hours apart of klonopin (clonazepam). Please discuss with your doctor/psychiatrist to discuss and gather more details before reaching a conclusion for a plan . Take care.

Could be either: Could be either - are these the symptoms that led to your taking Klonopin (clonazepam)? If so, may be breakthrough anxiety since for most people Klonopin (clonazepam) would have a longer duration of action.