question on parrots health

before you panic its not for me skys fine.
i know a mum at school who has a rescued amazon called milo i have seen him and hes a sweet little man.
well her question is which she asked me and now i'm asking the parrot owners on here.
milo for some reason seems to be hyperventailing every 6/8 weeks about the same time at night and she can't understand why.
he hasn't done this all the time it seems to be forming a pattern but as you can imagine scares her.
she covers his cage over which seems to help calm him down.
we ruled out enviromental stuff like fumes etc his cage hasn't been moved, nothing new has been introduced in his cage or near him, he is allowed out etc the same so its not down to increased exercise etc.
she said its as if hes scared of something and he goes very quite and still but shakes but can not find out why its happeneing.
could this be some thing to do with the fact hes a amazon etc or possibly a medical reason............there is a bird specialist close to us so she was going to give them a ring.
the only thing i can think of by the sounds of whats going off is panic attacks...........can parrots have panic attacks?
if so the only thing she can do is keep him quite and calm?
would like to know what you think i know its bothering her as milo is a special little man to her and has come along way.