[avaiptutt]

Does it even make sense to ask what the "I" is...

The Buddha spoke of the 'I' in many ways; that it is something the mind manufactures or fabricates. For example, the suttas use the terms 'I making' and 'my making'.

Below is one text where the Buddha called it an 'assumption':

There is the case where an uninstructed, run-of-the-mill person — who has no regard for noble ones, is not well-versed or disciplined in their Dhamma; who has no regard for men of integrity, is not well-versed or disciplined in their Dhamma — assumes form...feeling...perception...mental formations...consciousness to be the self.

That assumption is a fabrication.

Now what is the cause, what is the origination, what is the birth, what is the coming-into-existence of that fabrication?

To an uninstructed, run-of-the-mill person, touched by that which is felt born of contact with ignorance, craving arises.

That fabrication is born of that.

And that fabrication is inconstant, fabricated, dependently co-arisen.

That craving... That feeling... That contact... That ignorance is inconstant, fabricated, dependently co-arisen.

Parileyyaka Sutta