Through the years I've done several similar breathing sessions.
Reichian breathing and transformational breathing mostly. I guess 7 sessions in total. The first 3 in group sessions the last 4 in 1 on 1 sessions. They all ended in my body cramping up, My hands turn into claws, my face tightened so much the last few sessions they put a tube in my mouth so I could still breathe. All in all very unpleasant. Decided after the last one that this kind of breathwork is just not for me. No release or katharsis what so ever.

I never had such cramping up although I had some strong tingling sensations in my hands which could be felt as mild cramping but it was pleasant, strong sensation that are pleasant like when you are on a rollercoaster.

I read in some rebirthing book, cramping up can appear quite often when people have their firsts sessions but they see this as not something bad to be avoided but as a sign of trauma needing to be healed, as a gateway given by the body go go deeper into it and to be accepted and healed. But it seems it didn't went very well with you, don't know why, maybe the coach wasn't good enough or with enough experience and knowledge, but I don't know.

https://www.youtube.com/watch?v=luf069ocKak