In plain words
Bound by the action born of your own Svabhāva, son of Kunti, what through delusion you do not wish to do, you will nevertheless do helplessly.
Word for word
Bound, O son of Kuntī, by your own duty born of your nature, what you do not wish to do from delusion, that you will do even helpless.
The commentators
Bhagavadgītābhāṣyam
यस्माच्च —
स्वभावजेन शौर्यादिना यथोक्तेन कौन्तेय निबद्धः निश्चयेन बद्धः स्वेन आत्मीयेन कर्मणा कर्तुं न इच्छसि यत् कर्म, मोहात् अविवेकतः करिष्यसि अवशोऽपि परवश एव तत् कर्म ॥ ६० ॥
In plain words
And since —
You are bound, Kaunteya — bound for certain — by action that comes out of your own nature: the courage and the rest, exactly as described. Bound by your own action, the action that belongs to you. And the very deed you do not want to do, you will do — out of moha, out of a failure to discriminate — helpless, moved by a power that is not yours.
Close to the Sanskrit
And because —
Bound — bound with certainty — O Kaunteya, by action born of your own nature, that is, by valour and the rest as already described, by your own action, action belonging to you: that action which you do not wish to do, you will do out of delusion, out of non-discrimination, even though helpless, indeed under another's power — that action.