What is
baptism?
He said to them "Go ye into all the world and preach the Gospel to every creature. He that believes and is baptised shall be saved, but he that believes not shall be damned." - Mark 16:15-16
Baptism isn't something you do if you feel like it. Jesus said, "If you believe and are baptised, you will be saved." If somebody asks, "Well, if I'm not baptised, but I still accept Jesus as my Lord, am I saved?" If you truly confess Jesus as your Lord, you will get baptised because He said to do it. If Jesus is your Lord, you need to be baptised because you are in submission to Him.
When all the people were being baptised, Jesus was baptised too. And as He was praying, heaven was opened and the Holy Spirit descended on Him in bodily form like a dove. And a voice came from heaven: "You are My Son, Whom I love; with You I am well pleased." Luke 3:21-22
It is God's will that you are baptised in water after you have been born again.
"Then Peter said unto them, 'Repent, and be baptised every one of you in the name of Jesus Christ for the remission of sins, and you shall receive the gift of the Holy Spirit.'" Acts 2:38
REASONS WHY
Only those who have confessed that Jesus is their Lord should be baptised. The Bible doesn't say that it is for those who have signed up for church membership! It doesn't say it is for those who are in the Pastor's good books! People get baptised for a lot of reasons. Some get baptised because they believe it's going to save their marriage; some because they believe it's going to get them into heaven; some because they want to use the church for their wedding ceremony.
There are all kinds of reasons, but the one and only legitimate reason to get baptised is because you have made Jesus your Lord, Master and Supreme Authority of your life.