摇头摆尾

idiom

to shake one's head and wag one's tail; to look pleased with oneself; to act in a smug or self-satisfied manner

Originally describes animals (like dogs) wagging their tails happily when pleased. When used for humans, it often carries a slightly negative connotation of being arrogant, showing off, or being pleased with oneself over minor achievements. Can be used neutrally for animals, but often derogatory when describing human behavior.