throwing herself and loudly breathing/growling ?

I got my dog (2f) when she was a puppy and she always does this thing where she kinda throws/slams herself against the pillows of my bed or the back of a couch and growls or just breaths really loudly. Whenever she does this she starts out on her side then eventually ends up on her back and wiggles around while growling. It’s honestly funny to watch, but why does she do this?

I tried googling this and most places said that it’s a “last warning” before they bite/attack you. This definitely isn’t the case because if I go to touch her when she does this she welcomes it and does not try to bite me or anything (she has never bitten anyone at that)

Definitely not concerned about this, just curious!