Every so often, my upper arm starts twitching, not the bicep- but the area under the arm from the pit to the elbow. It continues for about 3 or 4 mins. I am usually relaxed watching TV, but it has happened in bed too.
I also get a lot of scalp itching in the back above the nape of my neck along the scalp ridge line. Only thing that calms it is cortisone anti-itch cream.

Facial tingling is a cardinal sign of low calcium levels. It is also sometimes too quickly diagnosed by doctors as "anxiety".

Twitching and muscle fasiculations can signal an imbalance of calcium and magnesium. Some drugs deplete calcium like the blood pressure drugs in the calcium channel blockers ( diltiazem and verapamil) and antiseizure (gabapentin/Lyrica included) drugs, because they block Vit D and calcium. People taking long term acid blocking drugs for GERD become low in calcium because they cannot absorb it anymore due to the low stomach acid (acid is required for absorption).

Some people who take SSRI/SSNI drugs long term develop a down regulation of dopamine as a side effect. This can lead to a tardive like movement disorder of the face/mouth and neck as well as leg cramping etc. This would include Cymbalta.

from http://www.ncbi.nlm.nih.gov/pubmed/9640489

Bruxism is clenching the teeth during sleep, which puts alot of stress on the facial muscles.

If you have been taking any SSRI/SSNI drug for more than a few months, it may contribute to movement disorders. Please discuss this with your doctor.