If he is generally tired also for no apparent reason, unexpectedly and suddenly, which can sometimes then lead to loss of consciousness, have his thyroid checked. My underactive thyroid, before diagnosis, led me to lose consciousness. Once it happened at the wheel of the car, once standing up in water (but not standing for long). Only by luck did I not get seriously mangled in the car or drown.

Mrrzy, I had to push and push to be taken seriously by an incompetent GP. Please get this sorted and do not take no for an answer.