It is often depicted that God like Vishnu sleeps and wakes after His sleep in Puranas?
Sleeping of God should not be considered like a ordinary task like
humans. It is called Yoga-Nidra. Lord Vishnu Himself tells the secret
behind this Yoga-Nidra in Gita Mahatmya: Chapter One. Please read it
below:
Lord Vishnu said, “My dear Lakshmi, I am not sleeping, but I am
watching how wonderfully My energy is working. It is by this wonderful
energy of Mine, by which I am controlling all things, and yet remain
separate (which is the leela of God who is one and only one). And it is
by remembering these divine activities or power of Mine, that the great
devotees and yogis manage to free themselves from the wheel of birth and
death, and attain that transcendental nature of Mine, which is eternal
and free from all qualities.”
Lakshmi said, “O, controller of all things. You are the goal of the
meditation of great yogis. Nothing can go on without You. And yet You
are separate. You are the cause of creation, maintenance and destruction
of all the material universes. Kindly inform me about the workings of
Your wonderful energies, which are so attractive, that even You are
lying here, meditating upon them”
Lord Vishnu said, “My dear Lakshmi, the workings of My multi-fold
energies, and how to become free from the bonds of birth and death, and
attain My eternal Nature, can only be understood by one of pure
intelligence, who has an inclination to render service unto Me. This
transcendental knowledge is fully explained in the Srimad
Bhagavad-gita”.