If you have something that is priceless and create others as individuals with free choice to share it with - is that being selfish?
If you beget a son and offer him as a sacrifice to save individuals who cannot save themselves – is that being selfish?
If your object is to share the glory that you already possess with those that have no glory of their own – is that being selfish?
Exodus 34:5 And the LORD descended in the cloud, and stood with him there, and proclaimed the name of the LORD. 6 And the LORD passed by before him, and proclaimed, The LORD, The LORD God, merciful and gracious, longsuffering, and abundant in goodness and truth, 7 Keeping mercy for thousands, forgiving iniquity and transgression and sin, and that will by no means clear the guilty; visiting the iniquity of the fathers upon the children, and upon the children’s children, unto the third and to the fourth generation, (of them that hate me – Deuteronomy 5:9).
Does God’s character seem selfish to you?
The Bible shows that God is not motivated by selfishness but by love.
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
Jesus gave his life for love.
John 14:31 But that the world may know that I love the Father; and as the Father gave me commandment, even so I do. Arise, let us go hence.
John 15:13 Greater love hath no man than this, that a man lay down his life for his friends. 14 Ye are my friends, if ye do whatsoever I command you.
God is the source of love.
1 John 3:1 Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not.
1 John 4:10 Herein is love, not that we loved God, but that he loved us, and sent his Son to be the propitiation for our sins. 11 Beloved, if God so loved us, we ought also to love one another.
1 John 4:16 And we have known and believed the love that God hath to us. God is love; and he that dwelleth in love dwelleth in God, and God in him.
Love is the basis of his commandments.
Matthew 22:37... Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. 38 This is the first and great commandment. 39 And the second is like unto it, Thou shalt love thy neighbour as thyself. 40 On these two commandments hang all the law and the prophets.
The Love of God is demonstrated in the life of his son.
John 14:9... Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father...
The idea of God being selfish is superficial and a product of the logic used to frame the question. The scriptures clearly show that God is motivated by love. It behoves us to take advantage of it while we have the opportunity.
Romans 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
I hope this helps.