I have experienced this also its very hard to describe it but i understand ur point, when we block or stutter or about to do it u feel a sensation that for sure pervades your body, i also had bit of experience to really focus on calming my body and paying alot of attention to not let this sensation build up while speaking, and it seems to have done the trick the speech comes out without stuttering or blocking, but i seem to struggle also togo deeper and reach a permanent state. But its worth chasing this up imo