I wonder if this might be as a result of anxiety. I have these kinds of reactions when I'm in a stressful situation. It could even be the case, I would suppose, that you're not necessarily highly stressed in your sessions; but you've developed this response to stressful situations outside of therapy & it's carrying over into your therapy sessions. I do know that it can be difficult to put what we feel on the inside into words. Often, it seems, the words just come out sounding silly (to us.) Perhaps you are responding to the difficulty you experience groping for the right words to express your feelings... just a couple of ideas off the top of my head, as the saying goes...

My last T used to keep some stretchy monster toys on a table. I didn't use them. But she said many of her clients would twist them unmercifully during their sessions. Perhaps having something to fiddle with while you are in session would be helpful?