Singing: Since you already enjoy singing and find it natural, continuing to develop your vocal skills could be a rewarding path. You can explore different vocal techniques and styles, and perhaps even take some lessons to further enhance your abilities.
Percussion: Instruments like the tambourine, shaker, or hand drum require minimal movement and can be a fun way to explore rhythm without the complexity of melodic instruments.
Keyboard: While the accordion may have been challenging, a keyboard or piano can offer a different experience. The keys are laid out in a linear fashion, which might be easier to grasp than the accordion's button layout. You can start with simple melodies and chords and gradually build up your skills.
Digital Music Production: Since you've already worked with FL Studio, you might enjoy diving deeper into digital music production. You can create complex compositions using virtual instruments and software without the need for physical dexterity.
Ultimately, the best instrument for you will depend on your personal interests and preferences. It's okay to try out different options to see what feels right for you. The most important thing is to have fun and enjoy the process of
making music!