This kind of happened to me. Dwelling mostly inside during the pandemic, I did a vitamin D blood test out of curiosity. Had critically low levels according to my doctor (something around 6, normal is between 30 - 80 AFAIK). Started taking vitamin D supplements a few months ago, and I'm subjectively feeling A LOT more motivated since.

But other than that, don't beat yourself up OP. Don't let your hobbies become chores. It's OK to just take the path of least resistance during your free time.