Baby gagging self for attention!!!

My 10 month old daughter has started this ridiculous thing where she shoves her hand in her mouth to gag herself, when I tell her to stop she laughs and continues doing it. It freaks me out. I'm paying attention to her, just cooking and she's in her high chair next to me when she does it. She doesn't do it any other time. How do I make her stop? It's frustrating/worrying me.