Hello, Its me again, It is another symptom of thyroid disorder, it will come and go, that is the first symptom that forced me to see an MD, after two Md's that just tried to prescribe anti-depressants and told me to stop drinking coffee, I was diagnosed with Hashimoto's by an Endocrinologist and he informed me that it was one of several symptoms of my thyroid disease, I alternate between Lunesta, and Benadryl. and when I feel right, nothing at all.