Lolita does this! It is funny, because she barks at the others to get them to play, to get them to move, to get their attention. Sometimes she barks at me, seemingly to get my attention, but for a reason that escapes me most of the time. Sometimes I think she barks to hear her own voice. Sometimes she will be sitting quietly, and she suddenly open a barrage of this kind of random barking, seemingly for no reason, as if it has been welling up inside her and has just erupted through her mouth. Perhaps it is too quiet for Her Puppiness who just can't stand the silence. I really don't know.
Sometimes, she is such a puppy!! Where is that coming from?