he write all this in 1st person present tense. he's talking about himself.
the opening paragraph of the chapter continues what he has been saying about the truth of every believer, that the body is dead but the spirit is life.
it's really awkward to try to force the things that follow in chapter 7 to be hypothetical pre-belief person-without-God business. it does not fit the narrative at all, and it contradicts the grammar.
in first person present tense he says, 'with his mind he serves God' -- is this talking about unbelievers? really?
there is a very clear, very straightforward thing being said. it is IMO the bias introduced by people whose doctrines have no room for the truth of this that tries to interpret it contrary to what it plainly says. many things in scripture are hard sayings, difficult to accept - and many things are mysteries, difficult to comprehend. the struggle of the flesh vs. the spirit in the life of a person who serves God in spirit but stumbles in the body is not a difficult thing to interpret, but it may be hard to acknowledge, and to accept.
it flows very naturally from ch. 1-5 and segues perfectly to ch. 8