I tend to do this with the first couple of mags when I haven't been shooting in a while. I am also a very flinch person when I get to the indoor range. I double plug and still jump the first few times I hear the guns go off around me.
It bugs the crap out of me, but I can't do anything about it. Once I start firing I am ok, but its always the first little bit till I get warmed up to it.