The Lord is never born, although He may show that He is going through the process of human birth. He never ages and never dies. Such a powerful Lord manifested at the home of Murti (Bhakti) and Dharmadev. He shows His body and actions to be just like those of all others. Those who understand His deeds to be divine, and understand that He never ages and is immortal, will be released from the cycle of birth and death.
(Lord Shree Swaminarayan, Vachanamrut Ahmedabad 4)

When the Lord appears on the earth in a human form, He possesses the same infinite spiritual powers that He has when He is in Akshardham. Only a foolish soul will think of Him to be a human, just like themselves. They believe that the Lord is born, then becomes a child, reaches adolescence, becomes old and eventually dies. However, these human features do not apply to the Lord. The murti of the Lord is divine. All His actions are
also divine.
(Lord Shree Swaminarayan, Vachanamrut Panchala 7)

On one occasion, Lord Shree Swaminarayan was seated amongst a vast assembly of sants and devotees. He asked them all a question.

“God incarnates on the earth for the salvation of souls. Is He unable to bestow salvation whilst remaining in His abode, without incarnating on this earth? God is able to confer salvation in whichever manner He wills. In that case, what is the purpose for God to assume a human form? If God can only bestow salvation after incarnating, but is otherwise unable to confer beatitude, this constitutes a deficiency in God. The fact is that God is able to grant salvation to souls, with or without incarnating on the earth. So what is the purpose for God to incarnate? That is the question.”

Lord Swaminarayan's meeting with the Mukta

All the senior and eminent sants answered the question in accordance to their understanding. However, Shreejimaharaj's remained unanswered because none of the answers were satisfactory. All the munis joined their hands and prayed, “Oh Maharaj! The answer to that question can only be attained from You.”

So Shreejimaharaj said, “The only purpose for God to assume an incarnation is that He surrenders Himself to the devotion of the devotees who have an intense love for Him. The Lord incarnates Himself and assumes a form in accordance to the devotee's spiritual desires in order to grant them His divine bliss. He then fulfils the spiritual desires of His devotees. As the devotees are corporeal and have human bodies, God also shows Himself in this manner in the world and assumes a human body. He showers affection upon His devotees. He conceals His greatness and takes the form of the devotee's son, companion, friend, or relative. Due to this relationship, devotees experience a close intimacy with God. A barrier between God and the devotee does not remain and God is able to grant His infinite bliss to the devotee according to their spiritual desires. Therefore, the purpose for God to assume an incarnation is to fulfil the spiritual desires of His loving devotees. Along with this, He bestows salvation to innumerable souls and establishes the religion (the decree of moral, righteous conduct).
(Vachanamrut Kariyani 5)