I am getting this also and I believe it is the release of toxins, not just "die off". I believe (if I am not mistaken), that often along with yeast die off toxins, that metals (mercury for example and other chemicals/metals) can be released from yeast cells also as they are dying.
Also take into account that as your body is dealing with yeast, other toxins may also be exposed in the process. The twitching/jerking (muscle tics) etc, maybe signs of that.