The statement signifies Siddhartha’s rebirth, his reawakening as a new person, unassociated with any caste, any group, or any past teachings and acquired knowledge. Now, Siddhartha is a new individual, ready to follow a new path, guided by his heart and his mind, to find the truth, not in the forest but amongst the people, in the daily grind.
Like the last forceful thrust of a mother in labour, Siddhartha is thrust into the world with a new vision of how he would attain his goal of salvation.
The last shudder of awakening is also suggestive of the yogic practice of kundalini awakening. Kundalini (Sanskrit: कुण्डलिनी) literally means coiled. In yoga, a corporeal latent energy similar to libido that lies coiled at the base of the spine. When aroused this latent energy can lead to Self-Realization through awakening of the “inner knowledge" that leads to "pure joy, pure knowledge and pure love."