This is something I have researched a lot for myself (I loooooove torts!)

For a proper indoor enclosure, you are going to want a space that is MUCH bigger than 36". More on the order of 8ft x 3ft.

The only tort I have found that you can keep in a small space (4ft x 2ft) is an Egyptian tort (Testudo kleinmanni), but that species is extremely sensitive and not considered a beginner species at all.

So, I would recommend the species people mentioned above, but you will need a big space to put a tortoise table habitat, plus an outdoor pen for the warm months.

This is why I don't have any torts I love them but don't have the space to do it up properly.