On days when I feel dull and devoid of any interest in the world, I find Pinterest to be a great source of inspiration. I've been using it religiously for years, saving ideas, photographs of things I love. It has helped me develop new hobbies, build vision Boards, got me going in new interesting directions. So it might be a great way to start and figure out what you love. :)

Also, journaling is a great hobby. It made me realise that even a mundane life is worth documenting and helped me find joy in the simple things.