Understand

If the self never acts, who is responsible for what you do?

The Gita insists the self is actionless — and still holds you to account.

One reading

The guṇas of nature do all the work; the ego, deluded, thinks 'I am the doer'.

BG 3.27 — All actions are wrought by the qualities of nature only. The self, deluded by egoism, thinketh: "I am the doer." read →
BG 13.29 — Seeing indeed everywhere the same Lord equally dwelling, he doth not destroy the Self, and thus treads the highest Path. read →
BG 18.16 — That being so, he verily who—owing to untrained Reason—looketh on his Self, which is isolated, as the actor, he of perverted intelligence, seeth not. read →

The tension

You are still told to act, to choose, and to carry the weight of choosing.

BG 2.47 — Thy business is with the action only, never with its fruits; so let not the fruit of action be thy motive, nor be thou to inaction attached. read →
BG 3.19 — Therefore, without attachment, constantly perform action which is duty, for, by performing action without attachment, man verily reacheth the Supreme. read →
BG 18.63 — Thus hath wisdom, more secret than secrecy itself, been declared unto thee by Me; having reflected on it fully, then act thou as thou listest. read →

My reading

"The guṇas act" (3.27) describes where compulsion comes from; it is not a permission slip. The Gita uses it to loosen the ego's grip on outcomes, then hands agency straight back: after laying everything out, Krishna tells Arjuna to reflect fully and then do as he chooses (18.63). Non-doership is a stance toward results, not an alibi.