Toddler keeps playing with belly button

My 21 month old daughter is always playing with her belly button. She pokes it, rubs it, pulls on it throughout the day and even at night in her sleep. She's done this for as long as I can remember. MIL said some people love the feeling of their belly button.. not sure if that's true lol, honestly I've always thought belly buttons were weird, certainly don't play with mine lol.

Does anybody else's bub love it? I don't think it's a "phase" because, like I said, she's always done it. I'm starting to get a bit paranoid and wondering if it's maybe a sign of something? Any help or tips to get her to stop would be greatly appreciated as it's sometimes quite red and raw :/