Honestly, there are too many potential causes to test. I may track my caffeine and whatnot but other things could affect it too. Its hard to test imo. For instance, there's been times I've went in to work with less than 5 hours of sleep and most of the time I wouldn't stutter, not even a little which is shocking but there have been other times with similar levels of sleep where I can't say one word without stuttering. I believe it's more of a psychological issue but I also don't know how to test my theory either. Another issue I've noticed is breathing and the speed at which I talk. The slow i speak, the less I stutter and the better I breath the less I stutter too, but sometimes that can give me a sore and tight chest by focusing on the breathing.