No person in the flesh is born again. If we were already born again, we could come and go as the wind – just as Jesus explained to Nicodemus. John 3:8 (NKJV), “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.”

We obviously have not received the spirit birth. However, we are begotten-again to a spirit life. In the Greek, “born” and “begotten” are the same word. The scriptural context determines how it should be translated. Therefore, this answer is explaining the difference between begotten-again and believer.

Romans 12:1(KJV), “I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service.”

The Apostle Paul is addressing “brethren.” These people believe in Jesus’s atoning sacrifice. Their bodies may be considered “holy” from God’s perspective. The only way we sinners can have a holy body is through the covering of Jesus’s blood.

However, as Paul wrote, the believers in Romans 12 had not yet consecrated their all to serve God. That is why Paul is urging these dear ones to take the next step. He is instructing these to present their bodies (or their human lives) as a sacrifice. 

We follow Jesus’s example. Jesus presented himself as a living sacrifice when he was baptized in the Jordan. Hebrews 10:5, 7 (NKJV), 5 “Therefore, when He came into the world, he said: (Animal) Sacrifice and offering You did not desire, but a body You have prepared for me.’ … 7 Then I said, ‘Behold, I have come – in the volume of the book it is written of me–to do Your will, O God.’”

When Jesus’ sacrifice was accepted, God begat him with the holy spirit to a life as a “new creature.” In the same manner, believers present themselves as living sacrifices and when God accepts their sacrifices, God begets them with the holy spirit.

Romans 6:4 (NKJV), “Therefore we were buried with Him through baptism into death (of our flesh), that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life.”

It is the new creature that walks in newness of life. Our lives at the point of begettal are devoted to living out God’s will. It will be through obeying God’s will that our minds and characters are transformed into Christ’s character-likeness. Romans 12:2 (NKJV), “And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.” This is the new life of a spirit-begotten person.

Additional Resources: 
Christian Questions Podcast
Episode #1324: “What Is the New Creation?”
The profound results of God creating something never seen before
Preview Video
CQ Rewind Show Notes

Episode #1110: “Are Christians Really Born Again?” 
Finding the true meaning and implications of being “born again”
Video Preview  
CQ Rewind Show Notes

Booklet (PDF) “What Everyone Should Know About Being Saved”