Vitamin defficiency? Are you spanish/italian or something that you all got narcolepsy? Or maybe you got gifted with diabetes? Diabetes makes you feel dizzy, sleepy, drunk and very sleepy after too much sugar, that is a decent test.

If not consider touching your body, your organs as much as you can, your balls and anything. My grandma started sleeping randomly despite being healthy in general but it turned out she had cancer and half more year to live. Considering she slept on morphine 20 hours a day heavily mentally impaired is not much of half a year of life.

Just suggesting. If it persists and you in general live a healthy life get your blood tested, cancer causes abnormalities in blood and if it really is abnormal in a way typical for cancer - get cancer markers or whatever it is called. If it is vitamins just get B6 B12 and magnesium.