This is determined by your own physical condition and health. Actually, don't care too much. Maybe your sleep quality is not good recently. Or the air in the classroom is turbid. Many people have been in a relatively closed environment, which is easy to cause hypoxia. It is normal for people to feel sleepy after lack of oxygen. You can exercise regularly and strengthen physical exercise. Don't stay in the classroom after class, take a few deep breaths outside. Take a nap for 20 minutes half an hour after dinner at noon, and have a small cup of coffee after waking up. Be on your guard if you have the following situations. It is quite possible that you are ill. When you go to the hospital for treatment in time, you are too sleepy during the day-this symptom has always existed and is usually the most obvious. Cataplexy-Cataplexy refers to the sudden or temporary disappearance of muscle mass, resulting in paralysis of the head or body without losing consciousness. It can last for a few seconds or minutes. Mild symptoms are vague language or stuttering, drooping eyelids or inability to hold things with your fingers. Severe cataplexy can lead to knee bending and make people collapse. Laughter, excitement or anger are typical reasons for falling down. The sudden relaxation of muscle mass may be the result of the brain suddenly entering REM sleep. Less than half of narcolepsy patients will collapse. Sleep paralysis-the so-called sleep paralysis refers to the temporary inability to exercise when people fall asleep or wake up. It only lasts a few minutes. Similar to cataplexy, sleep paralysis may also be related to insufficient transition between REM sleep and waking state. Sleep paralysis is related to hallucinations. Hypnotic hallucination-refers to images that are mentally like dreams, usually scary, and often appear during sleep or before sleep paralysis. These four symptoms are called sleepiness tetralogy and belong to the clinical manifestations of narcolepsy. Other common sleepiness diseases include sleep apnea syndrome, narcolepsy and nocturnal muscle contracture. The so-called sleep apnea syndrome is intermittent respiratory arrest during sleep, often accompanied by obesity, heavy snoring and high blood pressure. Most of the patients are adult males, and occasionally there are women or children. As for narcolepsy, that is, excessive sleepiness during the day, some patients will have paroxysmal syncope after excitement (such as laughing and coughing), and some patients will have hallucinations or paralysis during sleep. In addition, muscle contracture at night is an intermittent cramp of limbs (usually lower limbs) during sleep. Because the muscles of the feet are always twitching and sleep is disturbed, there is no way to enter the third and fourth deep sleep periods. When I wake up the next morning, I always feel that I haven't slept enough and I will doze off intermittently.