You are most definitely not alone. It even has a name: orgasmolepsy, or the presentation of cataplexy during orgasm. It happens to me, to varying degrees... sometimes barely or not at all, and sometimes it's like my full-on normal C.
It's very noticeable when you're... how to put this tactfully... by yourself.
As far as the thread topic, for me, I am pretty sure my C always has triggers. The worst is anger. And its presentation is interesting. It's not the thing that makes me angry that does it, it's me expressing my anger. The more intense the expression of anger, the rougher the C attack. Example of mild:
Child leaves backpack in the middle of the kitchen floor. Did it last week too. I call child into the kitchen, and if I let myself get mildly angry while lecturing I'll get a little droopy (non-intense, maybe half a second C, sometimes the kid notices). Have to be stern but CALM.
Example of bad:
God damn dachsund eats another shoe, half of a brand new pair, we're easily over $1000 into this little fetish of his. I scoop up the f****er and yell at him as I am escorting him outside and I have to stop and lean against the wall or fall over. Or get in an argument with GF over something and feel really angry/passionate about a response I am making. Arms fall to sides, speech slurs, knees start to buckle, need to lean on something. If I force myself to be calm it stops, but if I try to maintain it (the anger), then I'm fighting against the C and losing.
I do try to fight against it. Feel it coming on and try to retain control of my muscles. It's not very successful. When fighting it, the best analog I could give is that I feel like a gear missing every tooth but one. So I try to fight it and I can't; the gear is just slipping, but then it grips for a fraction of a second, which manifests as a sort of twitch, but then I have no muscles again.
I do think that some days I am more prone to C than others, and, if this makes sense... I can sort of feel it waiting in the back of my head/neck. Maybe that sounds weird. But I can say that if I have C happen today it will be of middling intensity. I think the intensity is linked to how well I slept the night before.
For me, cataplexy is not muscle weakness. It's muscle absence. It's as if the affected muscles are just not in my body anymore and I start to fold. It's getting worse too. I hate it so much.
Other, milder triggers are funny things - it's got to make me belly laugh and then I experience it mildly - orgasms as mentioned above - anticipation and then realization of something exciting - like standing at the edge of a doorway to scare my friend and then scaring him and C'ing as we laugh about it, mildly. Making an unanticipated witty comment that people laugh at does it a little bit too. I do a lot of public speaking and if I am in that zone, I can be funny and off the cuff and there is no problem. It's when I am, say, sitting in a class for training at work and something funny pops into my head and I say it and people laugh - get C then.
Such a crazy crazy thing.