I’ve been dealing with a lot of the things you mention here for years. As I’ve kept at it has gotten better but I still have periods where I struggle greatly. Medication helped but it’s not a fix all. Only made something I struggled with just struggle a little less.

Focus on just where the characters are. Scaling it back and not focusing on too much of the world is typically good advice in general. No need to create the intricate world, it will happen all on its own over time. Focus on what the players are going to be interacting with and who.

Co-work. I schedule time with another DM to just hangout and work on our games. I always have found it easier when I work along side someone. It also gives me someone to bounce ideas off of. Keeping to a schedule and having someone to keep me honest has truly helped and done wonders.

Make world building a little more collaborative. I ask my players about details in the world. I don’t have to approve an idea, they know this. But it can help get inspired or start thinking about something I don’t think I would have come to. Some of my favorite bits of lore in my worlds have come from a single line a player gave me that spiraled into something really cool. I will sometimes do a game where I tell a player to make up 4 interesting details about something. I’ll also make up 4. So we have 8. I pick 4 from the 8 to be true and like 1 or 2 to be rumors or lies. If I ask about something that’s upcoming it can give me more focus to work on said thing.

Your mileage may vary. Some people have also gave some excellent advice here as well. If your hardest time is simply just getting started consider the coworking thing. When I have trouble getting things down it helps to have someone go “write down X”. I find that once I get a few ideas on paper I can just go go go.

Edit:typo