A Writer's Block

I'm suffering from a writer's block/blackout regarding this campaign.

One side of the problem is that I don't know where to start or what, exactly, should I prepare. If I had a to-do list I would've be able to start working on it right away; but I don't know what to prepare for such a campaign. For a regular trader, exploration or even mercenary game I'd know exactly what needs to be prepared (mostly adventures and world-based adventure hooks), but this kind of high-level play is quite difficult to prep for, especially as its a roaming high-level campaign (so there isn't a permanent cast of NPCs as would be in, say, a palace).

Another side of the problem is that I'm not sure about the overall plot. Ideally this should probably be a political "sandbox", but on the other hand I don't seem to attach very well to the this setting's hooks.

And yet another side of the problem is the general GM burnout I appear to be suffering from in the last few months or so. So far it's mainly affecting our D&D game, but I fear that this burnout is causing problems with the preparation of this campaign.

Any advice for overcoming this burnout and this writer's block would be welcome.

Prep Considerations

A question which arises is "what should I prepare for such a campaign". A 'normal' trader campaign requires a starmap, UWPs, some plot hooks and passengers/patrons; but this one would be a political sandbox, so things would be different.

I was thinking about making one or two important NPCs per world, contacts if you will; each would have his or her motivations and his or her interests. Other than that, detailing the governments of each world using both Path of Tears and the MGT Factions/Cultural Quirks tables would probably also be useful.

Any additional suggestions about what I should prep would be welcome.