It's most likely a problem with your ears. I have the problem too. Some films seem to do LOUD LOUD LOUD ACTION and then very very very quiet talky talky scenes. You either have to be constantly fiddling with the volume, have it loud enough for the talking so too loud for the action (which is only bad if it's late and there's others in the house), or you have it quiet and put the subtitles on. All are not ideal.
Do you use your TV speakers?
Doesn't happen as bad with a decent kit.