It's great you've noticed the tendency, OP. And some good advice on this thread.
Re morning anxiety - our natural daily rhythm gives us a surge of hormones that helps us wake up - cortisol/adrenaline. I think if we're used to 'running hot' this can be even more noticeable.
Beyond all the really good advice for self care and health and lifestyle points (I'd suggest vitamin B, maybe magnesium, and maybe iron as well as Vit D) I wonder if it's worth sitting a bit with the feelings?
I recognise the downturn feeling you describe. Is it maybe at least in part a natural and normal response to the seasonal change?
I wonder if just more closely observing the change in pace, scene, feel and mood of the seasons might help?
Noticing the slowing and darkening. Knowing that there's nothing to fear in this change of pace. Finding ways to acknowledge and become less anxious about this different season.
Tradtitionally, we mark it by observing, and maybe some ritual to counteract the parts we find hard would be useful? Fairy lights, evergreen plants/trees, roots, preserves. Thinking of hibernation, more sleep, withdrawal, reflection, cosiness, stillness.
I like knitting, felting, reading, maybe preparing some bulbs, planting seeds, or clearing ground. Gardening is always a great way to ground and calm, and there's lots to be done in winter.
Cold water swimming is great, but I appreciate not for everyone! Lighting fires, writing cards, reading/writing poetry, pets, volunteering ... loads of things we can do that I think are comforting and nourishing and help us to appreciate the season.