Cats usually purr when they are in a relaxed and comfortable state, but if a cat keeps purring, it may be a sign of physical discomfort or disease. Here are some possible causes: 1. Oral problems: Periodontal disease, canker sores, or other oral problems may be causing your cat to purr incessantly. 2. Respiratory system problems: Respiratory system diseases such as asthma and pneumonia may also cause cats to purr.

3. Nervous system problems: Nervous system diseases such as stroke, encephalitis, etc. may cause cats to purr abnormally.

4. Tumors: Tumors in the mouth or throat may cause cats to purr continuously. 5. External factors: Such as inhaling harmful gases, accidentally eating toxic substances, etc. may also cause cats to purr continuously.