Perhaps he mulled the questions and answers over, for John  7 tells us he defended Jesus when other Pharisees accused him: "Does our law judge a man without first giving him a hearing and learning what he does?" But John still does not say he believed.

Then, unexpected, John 19 shows Nicodemus performing an act of great faith.  When Joseph of Arimathea took Jesus' body down from the cross, Nicodemus came with expensive spices and helped anoint the body for burial. According to Hebrew law this made him unclean, he could not celebrate Passover. Further, it publicly identified him with Jesus when even the disciples had fled.

I wonder when Nicodemus decided to believe in Jesus --- in a blinding moment, or by a slow process of growth?

Father God, thank you for your saving grace.  Now take all of me, for your glory.  In Jesus Name I Pray. Amen and Amen

 ¹ There was a man of the Pharisees named Nicodemus, a ruler of the Jews. ² This man came to Jesus by night and said to Him, “Rabbi, we know that You are a teacher come from God; for no one can do these signs that You do unless God is with him.”
³ Jesus answered and said to him, “Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God.”
⁴ Nicodemus said to Him, “How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?”
⁵ Jesus answered, “Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. ⁶ That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. ⁷ Do not marvel that I said to you, ‘You must be born again.’ ⁸ The wind blows where it wishes, and you hear the sound of it, but cannot tell where it comes from and where it goes. So is everyone who is born of the Spirit.”
⁹ Nicodemus answered and said to Him, “How can these things be?”
¹⁰ Jesus answered and said to him, “Are you the teacher of Israel, and do not know these things? ¹¹ Most assuredly, I say to you, We speak what We know and testify what We have seen, and you do not receive Our witness. ¹² If I have told you earthly things and you do not believe, how will you believe if I tell you heavenly things? ¹³ No one has ascended to heaven but He who came down from heaven, that is, the Son of Man who is in heaven. ¹⁴ And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up, ¹⁵ that whoever believes in Him should not perish but have eternal life. ¹⁶ For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. ¹⁷ For God did not send His Son into the world to condemn the world, but that the world through Him might be saved.
¹⁸ “He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God. ¹⁹ And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil. ²⁰ For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed. ²¹ But he who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God.”