It’s crucial to get up early, because the Namib Desert is hot, and you best get your sightseeing done before the sun sizzles at volume 10.
The cooler front and back ends of the day are also the best times for photography, so there’s no excuse for sleeping late. In any case, everyone around you in the campsite at Sesriem will be starting up their cars.
Camping in the park means that you can enter the Namib-Naukluft National Park a full hour before the people who are staying outside the park. And you get an extra hour after sunset, too.
Start early and max out your day!