I’ve seen this happen with some species of wild caught dragons that appear to 'play dead' to escape once captured. The eyes roll back, the whole body stays still and goes somewhat limp, you tend to relax your grip, then all of a sudden they ‘come back to life’ and bolt or struggle violently to get away. I don’t know if it is related to that, but it might. Either way, as Oshkii suggested, it is likely due to the dragon being ‘nervous’ (i.e. feeling somewhat stressed). If it is not used to being handled, that would be enough to stress it a bit.
Size-wise it looks good. Adult SV length is 10 – 11cm in these guys.
In nature, like other sand dragons, this species basically breeds and then dies. However, in captivity their average life span is 5 years or so and occasionally a bit longer, as stated.