Is “believing” a “work” according to Romans 5:4???? Yes or No ——
If your belief comes from God, then it is not a work of man, but a work of God. If you came to your belief on your own without the direct intervention of the Holy Spirit, then your belief (such as it is) is a work and it will not save you.
Did God draw you to him?
Is your belief the product of God directly intervening in your life to bring you to a saving faith in Christ?
Or is this something that you did on your own?