My 3 year old won’t stop shaking his butt and private parts on me😒❗️

My son is 3 almost 4 years old and constantly shakes his butt and private parts on me, or anyone in my family. He does it all throughout the day and laughs!! I’ve tried whooping him, ignoring it, talking to him about it..and he just continues to laugh and do it!!! He doesn’t go to school or day care, and the only other person that has watched him is my mom. But I’m scared to take him in public or for him to go to school doing this!!! Someone please help bc I’m literally at my breaking point with him doing this!!!