some medications cause those reactions durring sleep. Are you taking any hypnotic type drugs, seditives or antidepressants also some pain meds and um marijuana.
Part of fibro is sleep problems so alot of the time we have to take meds for sleep. My Dr. tried a couple that made sleep time very freaky. Ambian works really good I had no side effects from that. But when I swiched to Kiaser they didnt cover it, now I take lorazapam..works great too. Fall asleep fast and stay asleep.
If you arent taking any meds and are having this problem I think you should talk to your Dr.