Muscle spasms

Whenever I have a session I eventually develop muscle spasm. They are usually centered in my upper thighs or buttocks. They don’t bring any sensations and are really distracting because the uncontrollable shake kind of throws me off and makes it difficult to concentrate. I’ve found that if I try to control them they stay pretty much in the same place but if I don’t do anything and let go it turns into a full body shake.

Is there any way to fight this off? Should I keep going until they go away? I’ve tried changing positions but they still come.