Hello George,
I like this idea of "initial experience of incompletude or "inability"
It sounds as if the first thing a baby experiences is a lack of competence. When hungry the baby experiences an uneasy situation which only can be ended when some substance passes through its mouth. It this, a baby is totally dependent on the mother who is the only provider for this substance. Suppose a baby can value this dependency in two ways: Either as an unpleasant shortcoming, or as a pleasant way to communicate with that still vaguely familiar "being" that not only provides for nourishment but also for comfort and warmth.
I am almost at the point that I am going to write my essay on "how I developed my first sense of inferiority". My lifestyle tells me that I must have experienced it as an unpleasant shortcoming, although..although.. "Everything can be totally different", as Alfred Adler used to say ("Es kann auch alles anders sein")
Paul