Yeah man definitely normal! I think your emotions, beliefs and cognitive factors play a huge role into the stuttering. Those things are also related to different situations. Personally I don´t stutter a lot when there is loud noise, i thought how is that possible? Then I realised it could be because I´m subconsciously and also conciously afraid to show my stutter. So when there is loud noise, I subconsciously know that people won´t notice my stutter much. Lots of things play a big role and change the way you talk.