For myself, I can say that I wake up with the sun, both in winter and in summer. I don't notice the difference between the seasons.
I think the main reason is the discrepancy between the daily routine established by a person and the daily rhythm of the body, regulated by hormones, including those dependent on sunlight.
It does not become for me, the morning comes later. But getting up until the morning can be uncomfortable and chilly. Fish oil won't hurt to compensate for insufficient sun.
The reasons may be different, including those mentioned in the question. In winter, in the morning it is most often still dark, because of this, the sleep hormone melatonin continues to be produced, which prevents the onset of vigor. This can be a banal lack of sleep, just fatigue, etc. However, if the property manifests itself exclusively in winter, then you can try in tandem with an alarm clock to use a light bulb with a timer and a function of a gradual increase in the glow. A kind of personal Sun, which will start its work in 20 minutes of the alarm clock.