The cat's limbs are stiff and unable to move, and it has been lying down. There are many possible reasons, including but not limited to neurological convulsions, hypoglycemia, poisoning, cervical spinal cavity or intracranial problems, etc. These are serious conditions that require diagnosis and treatment as soon as possible.

First of all, if your cat is in this situation, it is recommended to contact the veterinarian immediately or go to the pet hospital for examination. Your veterinarian will perform a detailed physical examination and may also need blood tests and imaging studies (such as a CT or MRI scan) to determine the specific cause of your cat's illness.

While waiting for medical treatment, you can try to keep your cat warm and gently massage its neck and spine to promote blood circulation. Note, however, that these procedures should be discontinued immediately if the cat shows signs of pain or discomfort.