Hi Cathy...I sounds like it could be BPV to me. They thought that is what I had a first but it ended up being Meniere's Disease which is more than positional. Fluid can collect in the middle ear, especially when you are laying down and causes equalibrium to be disturbed. If the vertigo only lasts a few seconds, that could be what it is. (BPV) I have to stay away from salt as it promotes fluid build up in the ear as well as other parts of the body.
Donna