What prompted Ramana Maharshi for his self-enquiry?

Answer 1

As a boy, Ramana lived in a small village in Southern India.  His father was a well regarded lay legal practioner.  When Ramana was about 12, his father died suddenly and without warning.  Quite naturally, Ramana began thinking about death.  When he was thirteen, he was suddenly gripped by a 'violent fear of death," and instead of doing what one might expect -- trying to find help, crying out for help -- Ramana lay on the floor, and in his own words:

... at once I dramatised the occurrence of death. I lay with my limbs stretched out still as though rigor mortis has set in, and imitated a corpse so as to give greater reality to the enquiry. I held my breath and kept my lips tightly closed so that no sound could escape, and that neither the word 'I' nor any word could be uttered. 'Well then,' I said to myself, 'this body is dead. It will be carried stiff to the burning ground and there burn and reduced to ashes. But with the death of the body, am I dead? Is the body I? It is silent and inert, but I feel the full force of my personality and even the voice of I within me, apart from it.

Wikipedia: Ramana Marhar

This spontaneous investigation, actually created on the spot by Ramana, was a form of the spiritual methodology known as self-inquiry, which is the seeking of liberation through knowledge of truth, most especially the truth of one's own actual nature. Ramana's mother was a practitioner of an ancient method of self-'inquiry known as neti-neti in which the practitioner cultivates a vivid and distinct conscious awareness of all manner of experience that constitute the living of the life -- thoughts, emotions, bodily functions, bodily secretions and excretions, pain, pleasure ... -- all the while addressing the content of the passing parade of phenomena with the judgment: not this, not this (neti, neti), seeking to rule out as one's actual nature each possible candidate one by one. It seems quite likely to me that Ramana's familiarity with his mother's sadhana might have influenced the course he took in his investigation.