It could be due to the stresses of life, or alteration in work habits. That may lead to an increased susceptibility to pain perception. We normally are always facing painful stimuli but our brain doesn't necessarily pick up the stimuli all the time. There may be an inherited perceptibility to receive pain. It may have to do with sex.
Males seem to be less susceptible to pain.
It occurs in men, it's more common in older patients than young patients. It is more common in certain ethnic groups than others, although it occurs in all ethnic groups. I'm not a sleep expert. I'm a rheumatologist but indeed, there is evidence that melatonin helps with jetlag and sleep patterns. To begin with, the treatment should include education and patient reassurance, explaining this is not fatal and what it really is.