The doctor, Animesh Mondal, has since apologised to the family, saying he could not find pulse or heartbeat when he had examined the patient.
Forty-year-old Mamata Sarkar had been admitted late last night in a critical condition.
This afternoon, her condition deteriorated and she was on the verge of collapse. That was when Dr Mondal, who was the attending physician, certified her dead, hospital sources told Press Trust of India.
The family was duly informed. But when they went to collect the body, they found the "corpse" moving its hands and feet.
Ms Sarkar was immediately examined and shifted to a cardiac care unit. Doctors said her condition is still critical.
Action will be taken against the Dr Mondal for negligence, hospital superintendent MA Rashid has said.
The government hospitals in Bengal come under frequent charges of negligence -- infant deaths are a common occurrence and last year, four health workers were suspended for administering Hepatitis B vaccines to children who came for pulse polio drops.
The health portfolio is handled by Chief Minister Mamata Banerjee.