So, I know this GJ is made to  be more accessible to first-timers, and I have some Game Dev experiences already. But my above mentioned mental problems makes it hard to join a group and keep conversations. Is this still recommended for someone like me, or not?

Sure. Develop it solo, then submit it. I am doing it solo. I code in teams regularly, but have never made a game with a team.

The nice thing about a game jam is that it's absolutely a setting where it's okay to experiment and mess up. MFGJ in particular is designed to be inviting for new developers, so I think it'd be a great place to start.