Children masturbating

Jo
I really wasn't expecting this until age 5-6 but today my 17 month old kind of sat down on her sippy cup and it rolled a bit and so she liked the feel and kept trying it back and forth. I'm pretty certain it was for the feels. She then got angry because she couldn't coordinate well enough and I was like, sweetheart you're on your own with this one lol. 
I'm certainly not about to shame her for this but I'm wondering if anyone else is seeing this so early and any pointers?