What kind of lighting do you have? I remember reading something about a lack of UVA radiation causing strange behaviour, but exactly what kind of behaviour was not specified.
He appears to be attempting to bury himself. Some tortoises will do so near or under a light/heat source in order to absorb more heat while being safely buried. Many of my young tortoises bury themselves near their basking light. Based on the enclosure there really isn't any adequate shelter that would make him feel secure. The over hang at the far end is too tall and lets in too much light. Most tortoises prefer a shelter that isn't much taller than they are and dark.
It's UV-B that is most beneficial to tortoises, UV-A does little positive for them. A lack of either would not cause strange behavior but the lack of light itself will cause a change in their routine.
my sully did the same thing.. then i put him outside, he went over to the corner of a boulder and a rock, and started doing it, completely buried himself rofl.. they just love digging :3