I have six Chihuahua's and out of those six only one of them has an issue like that but once in a while I will suddenly notice the absence of Giacomo. When I find him he is usually sitting in a corner somewhere acting very timid and trembling. He doesn't have a seizure or anything he just acts like he is terrified. None of the other Chihuahua's or Bella the Yorkie appear to act any differently so whatever it is bothers only Giacomo. I agree with the Boopster about how to react. I don't want to reinforce the behavior so I just pretend I don't notice and continue with what I am doing. If he wants or needs me I allow him to come to me. At some point he tends to come around and bounce back to normal.
So far I haven't been able to pin point any activity that triggers it. In fact the other day my hubby and I were saying "maybe he see's ghosties"
