Lately, I've been noticing that my tegu, Anasi has been doing this wierd thing while she's burrowed and sleeping (or trying to sleep) where she shakes her tail, like the last 3 inches of it like a rattlesnake a few times, 3 or 4 times maybe for a few seconds. And only her tail is exposed, she's burrowed and this has been happening once a night for the last 3 nights or so. Any idea why this is?