When my 1 month old went in for his 2 week check up the doctor told me that quivering is completely normal. She didn't say why exactly though. Just a call to the pedi and I'm sure they'll explain. This should help also: http://www.parksidepediatrics.com/eResources/Newborn/AppearanceandBehavior/tabid/123/Default.aspx
visit ur nearest audiologist and go through Brain Stem Response testings to see whether its a cranial nerve impairment or not coz such symptoms may be sometimes due to some cranial nerve disfunctioning.
That is totally normal. Both my children did the same thing.