Hi MSBee - my 2 cents on the subject - I have Uhtoff's syndrome and when I over do, which is quite often (Taffy I don't need a lecture!) I sometimes get spasms similar to what you are describing when I get overheated or my body core temp gets too high. It's happened a couple of times. It's kind of scary, especially the first time. I just make sure I stay hydrated.

If you are on one of the interferons and this happens, it could be a reaction. They can happen no matter how long you've been on them.

Rest and get plenty of water!

Welcome to NT!