Here it is very plainly explained that God is not responsible for the living entity’s accepting different types of bodies. One has to accept a body according to the laws of nature and one’s own karma. Therefore the Vedic injunction is that a person engaged in material activities should be given directions by which he can intelligently apply his activities to the service of the Lord to become free from the material bondage of repeated birth and death (sva-karmana tam abhyarcya siddhim vindati manavah). The Lord is always ready to give directions. Indeed, His directions are elaborately given in Bhagavad-gita. If we take advantage of these directions, then in spite of our being conditioned by the laws of material nature, we shall become free to attain our original constitution (mam eva ye prapadyante mayam etam taranti te). We should have firm faith that the Lord is supreme and that if we surrender to Him, He will take charge of us and indicate how we can get out of material life and return home, back to Godhead. Without such surrender, one is obliged to accept a certain type of body according to his karma, sometimes as an animal, sometimes a demigod and so on. Although the body is obtained and lost in due course of time, the spirit soul does not actually mix with the body, but is subjugated by the particular modes of nature with which he is sinfully associated. Spiritual education changes one’s consciousness so that one simply carries out the orders of the Supreme Lord and becomes free from the influence of the modes of material nature.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 02 – Text 41