Some suggestions:
* Spend a little time thinking about what you're hoping to get out of this break. Try to come up with some concrete goals. Write them down. It doesn't necessarily have to involve an extensive to-do list, which might feel overwhelming. But maybe a handful of goals related to your mental or physical health?
* Do you rent or own your home? Can you sublet or rent out? Consider spending at least some of the time in a different part of the country. If there's some place that interests you and has lower cost of living, all the better.
* Let you professional network know about this. And try to find some time to reconnect with colleagues and friends during this period. This will likely help you when you're ready to return to work.
* Be mindful of the fact that you are in a position that is unattainable for practically everyone else. Very, very few people have the financial means to stop working for an extended period. Don't take the break for granted.
* Traveling can broaden your horizons, but it also has a way of helping you better appreciate what you have at home. As Chesterton wrote, "The whole object of travel is not to set foot on foreign land; it is at last to set foot on one’s own country as a foreign land."
* I'm not sure where your interests lie, but one important contributor to personal fulfillment is helping others. Consider looking for opportunities to volunteer.
* A lot of people think burnout is purely a result of being overworked. But researchers who study burnout point out that there are two other contributors: cynicism/detachment and inefficacy. Basically, if you're not finding meaning in your work, and you're not seeing the fruits of your accomplishments, that can burn you out even if you're not particularly overworked. So when it's time to return to work, be on the lookout for these things, because you don't want to go through this cycle again.