“Are you looking for something?” is what I would say. It’s difficult to explain the difference. I will try the best I can. “Are you looking for something?” more or less means “You seem to be looking for an object - is that correct?” I believe you will rarely come across “Are you looking for anything?”. To be looking for anything would to me literally mean that it doesn’t matter which object you find as long as you find an object. But in other contexts it would be common to say "Are you looking for anything specific/special/else?" Hmm...The more I think about this question the more unsure I become. Think about this: “I like any kind of music” means “I like all kinds of music” “I like some kinds of music” means that there are some kinds you like and some kinds you don’t like. “Are you hearing anything?” means something like “Can you hear something? - it doesn’t matter what you hear as long as your hear something” I hope this helps.