It is completely natural to wake early, just as it is to be an evening person.
This can sometimes occur due to anxiety or anticipation about the day to come. I know that when I am aware of a need to be up earlier than normal, I overcompensate occasionally by waking up too early. An example, is me having a meeting on a Saturday morning, my usual schedule would be Monday to Friday, waking up at 7am, then having lie ins on the weekend, waking up around 11am. On these meeting days I must wake up at 6:30am. The night before, I prepare my things, and during this time, my subconscious decides that I will become focussed on waking up on time, and as a result, I may have disturbed sleep, maybe waking at 4am, and then 5am. Think of it in the way you'd expect on the night before christmas, your birthday, or an important exam. High arousal, whether that be excitement or anxiety, you will be almost too ready to wake up, so will wake up too early.
Alternatively, you may have too much light or noise in your room, or go to sleep too early. For these may I suggest you have curtains or sleep facing away from light sources. Noise is more difficult, maybe consider not having alarms that go off periodically from an early hour- if you need to set it, maybe have it go off every 15 minutes from 7am as opposed to on the hour every hour from 4am for example. Your body does not need too much sleep, so will wake up when ready, maybe consider going to bed later, maybe using more energy exercising and such, and go to bed when you feel sleepy, or are yawning more frequently.