It's normal for cats to be less active after a bath.
It's quite normal for cats to be lethargic after a bath, as most cats are afraid of water and may feel frightened during a bath, leading to listlessness afterwards. This usually doesn't last long; with gentle comfort, the cat will recover within a day.
If your cat develops a fever or runny nose after a bath, it means it has caught a cold and needs immediate treatment. When bathing your cat, be sure to keep it warm and dry its fur thoroughly afterward; otherwise, it's prone to catching a cold and developing skin diseases.
