My baby has red marks all over ...

So my daughter is 6 months old; however, she’s been doing this things for a while now...maybe at the start-middle of 4 months old. It’s just really excessive now.

.... She love to like grab/scratch and hit her stomach. A LOT. like she has red marks alllll over her torso and it looks like she’s almost been beat or something (I know that’s awful). She’s such a happy baby, and no it’s not like she is itchy or anything, it’s just kind of a thing? Like I’m not sure if it’s her been so excited that she just doesn’t know what to do with her hands?

I don’t know if there’s an underlying soemthing it could be? My only idea...if it’s okay to say, is maybe she might have a problem? Could this mean she may be autistic in some form?? I don’t mind...just curious if any other mommas went through this??