What to make of arousal "jolts"

Been into prostate play, aneros, mindgasm for a couple of months. Feel like I am getting good results and am optimistic about this forum's approach. One question: when aroused, by porn, audio or just mental images, I often if not always experience a "jolt" that almost feels like a spasm. Muscles go tense and I jerk (upwards?) Definitely involuntary but in no way like a gentle wave. I can say "yes" to these feelings and begin writhing or convulsing on the bed or chair with arousal building. But there has been no release. The feelings are definitely pleasurable and would normally lead me to fap. But I have not done so for about a month so am easily aroused. My focus has been on "rewiring" with attention on the prostate. I know how to do relaxation and am able to become quite relaxed but these "jolts" are anything but relaxing. Any thoughts?