Q. Can you explain why Jesus did not get baptized until approximately 30 years old?
A. What we call baptism is the Christian version of the Jewish Mikvah, or ritual bath. It was a ceremonial act of preparation performed for various occasions such as the Sabbath or other Holy Day, entering into marriage, or consecrating oneself to the Lord. John the Baptist, after whom the Christian baptism is named, had Jews take the Mikvah as a sign that they were repenting of their belief that their own works could save them, and were ready to receive their Redeemer. Later, Christians were baptized as a sign that they’d accepted the Lord as their savior and the baptism became the symbol of the death and re-birth.
Some protestant denominations baptize infants, but this is really an act of dedication by the parents and is not meant to replace the adult baptism wherein one makes a public declaration of faith.
Jesus took the Mikvah at the outset of His ministry when He was 30 years old. Since He had nothing to repent of, it could only have been an act of consecrating Himself at the outset of His ministry. It was most certainly not His first Mikvah, since as an observant Jew He would have taken one before every Sabbath and Holy Day since He reached the age of accountability.