What causes one to have a sudden hiccup type inhalation like half a hiccup w/o having the hiccups.?

Half a hiccup?: You are describing a partial hiccup - which could be caused by the same mechanisms that cause hiccups, but with a less severe form. A hiccup is a sudden spasm of your diaphragm (breathing muscle). You may be having a smaller spasm that is just half a hiccup. Treatment of hiccups can be difficult, but fortunately, they usually go away on their own.