The winter is rough for a lot of people. Sometimes accepting that you're going to be sluggish for a while is one of the best things you can do. It's frustrating, but being sluggish with acceptance is better than being sluggish and tormenting yourself over it. It's ok if the Christmas tree never gets put up.
If you can take what little energy and motivation you've got and focus on doing only things that in turn enhance your energy and motivation, that's best imho. I can make suggestions about what sort of things qualify, but you'll have to decide for yourself.
Taking a brisk walk just below the level of breaking a sweat can help. You also don't have to force yourself to do it, only if you feel in the mood. Yoga can also be a good winter time indoor activity.
Dietary changes were really helpful for me, and easy to implement. Not consuming anything served cold or raw, and trying to eat mostly freshly cooked foods worked wonders for me.
You might want to get your vitamin d levels checked by a doctor if you'd never had that done.
The info in these links might be helpful:
Chinese Herbal Medicine and Acupuncture, World's Second Largest Medical System
Self-Treatment and Miscellaneous