Several conditions might induce sudden tiredness. Narcolepsy, a neurological illness that causes daytime drowsiness and abrupt, uncontrolled sleep bouts even while talking or eating, is the most prevalent. Sleep apnea, when breathing disruptions during sleep induce daytime weariness, is another possibility. Inadequate or poor-quality sleep may also cause excessive fatigue. Stress, despair, and worry all disturb sleep. Vitamin D, B12, and iron deficits may produce weariness and sleepiness. Medications including sedatives and antihistamines may cause sleepiness. Modalert (modafinil) may assist with excessive tiredness. However, a doctor must diagnose and treat the reason of the drowsiness.

https://www.smartfinil.net/product/modalert-200/