Like, there's tons of philosophy to the question "what is (the) I".
I like the buddhism answer that the I is only an idea, and therefore non-physical and timeless. The material just flows and sometimes happens to be in one shape and another. The consciousness, which we perceive when we see something, is more like a dream that shouldn't be taken too seriously.
There's a Zen riddle to that: (riddle of the wind)
Two student monks were standing in front of a flag that was moving in the wind.
The first monk said: The flag is moving.
The second disagreed: No, the wind is moving.
Along the way came the zen master.
The students asked him: Is the flag moving, or is the wind moving?
Upon which the master replied: It is neither the flag that is moving nor the wind that is moving; It is the soul that is moving.
It reminds me of a bit in the outer chapters of the zhuangzi that's talking about fearing death. It points out how bad a lump of iron would be if it demanded to only ever be a knife and never recast into anything else.
How am I to know that the current configuration of the molecules I'm made of is the best use of them? There will come a time where everything that's me is recast and put to better use.