3month old sucking hands?

My little girl has just turned 3mo and has recently started constantly sucking her hands, i no its not when she's hungry as she does it after feeds etc and she seems so content and happy when doing so. She has never had a pacifier, but i have recently tried her with one 2 c if she will stop using her hands but she just spits it back out. Its not something im worried about, would just like to know if this is normal.