Our 12 week old girl will randomly get puffy and scared for what seems no reason. she has done this from the time we got her at about 7 weeks. sometimes we will be walking and she is in attack mode and she will do it, other times we might startle her by walking past but other times, we are lying in bed, sitting on the couch ect. and here she comes all puffy, back arched, walking sideways, half lunging at us. my husband and i look at each other like "does she not likes this movie or something?". we know she is still quite little and extremely playful but is this normal?