According to an article on menshealth.com, sleep apnea, an underactive thyroid, adrenal insufficiency, chronic fatigue syndrome, anemia, diabetes, along with clinical depression and endocarditis can all be the cause of fatigue.
Fatigue is extreme tiredness that usually results from a mental or physical exertion or even illness. It comes in many different flavors as some would say.
Ways that you could fight this could be by warming up before you start your day and giving yourself a few minutes. Breakfast can also come a long way instead of skipping meals. Becoming active is also a plus and get that body moving!