When do babies start putting a pacifier in their mouth by themselves?

My daughter is 5 and a half months old. She learned to grab her pacifier from me if I held in front of her when she turned 5 months. Now, actually I just noticed it last night, that if she spits it out while she's asleep and wakes up she'll rub her hand around on the bed trying to find it. If it is within reach she'll put it back in her mouth. but most of the time I have to do it for her because she cant find it or she'll try to put it in backwards.