Hi Mufad and All,
Sorry I'm late to this thread, but I have been away for the summer.
I experience single sudden breaths also sometimes during meditation, but in my case they are outgoing, and happen when the breathing gets very faint and the mind is turned inward very much and unaware of the breathing and other physical sensations. It's interesting why for some people they become outgoing, and for some, like in your case, incoming. But I suppose that can change over time for the same person as purification goes on.