Upvote:3
Yes You can (or could), because I did it in 2011 and visited many of the same places as the Grand Tour trio did - go do it, its fun. Just dont break down or get lost - Namibia is a lovely but huge and desolate place.
Upvote:4
There are no restrictions, according to the official Namibia Tourism, and exploring by car is encouraged as the best way to see the country. It offers detailed route maps available in multiple formats (online, pdf, high res e-mag). You do not need a permit to drive on the sections of beaches where it is allowed and posted; in some areas there are dedicated paths you must use. To rent a vehicle, you would need your national driving license, along with an International Driving Permit (IDP) (translated to English if your home country license is not).