Talking from my experience btw 
Have you ever gone to bed at 2 or 3 AM, expecting to sleep until late morning, only to find yourself waking up naturally at 6 or 7 AM? Even more surprising, some people are unable to fall back asleep despite getting far less than the recommended 7–9 hours of sleep. At first glance, it may seem like your body simply needs less sleep. However, some scientists suggest there are several possible explanations.
One possibility can be the circadian rhythm, the body’s internal biological clock that regulates when we feel sleepy and when we wake up. If your circadian clock is strongly set to wake you up at a particular and exact time, it may do so regardless of how late you went to bed. Another explanation can be sleep debt and stress. High levels of stress or anxiety can increase hormones such as cortisol, sometimes called the stress hormone. Elevated cortisol in the early morning may cause people to wake earlier than intended, making it difficult to return to sleep.
Lifestyle factors can also contribute, including:
- Excessive screen time before bed.
- Caffeine consumption late in the day.
- Irregular sleep schedules.
- Academic or work-related stress and depressed mindset
- Exposure to light early in the morning.
In some cases, consistently waking after only a few hours of sleep may be associated with sleep disorders, such as insomnia or circadian rhythm sleep-wake disorders. However, occasional early waking does not automatically mean someone has a medical disorder.
Sleep is not just about how long we sleep—it is also about sleep quality, sleep cycles, and maintaining a healthy biological rhythm. Some people can take short nap or power nap between their night shift works so that’s the ability of some people that they can do so.
Have you ever experienced waking up after only 3–4 hours of sleep without an alarm? Do you think it’s simply your biological clock, or could it be an early sign of a sleep disorder? I sleep at 2-3 am and still wake up at 6-7 am idk why.
MBH/PS