Hi Spiny,
If your perception is that you dream 'early' in your sleep cycle and if you have any other symptoms suggesting dysregulated sleep or sleep deprivation, it may be worth getting sleep study. Rapid onset REM-stage sleep is a classic feature of Narcolepsy, or if you feel like you 'dream all night' it could a result of repeated arousals during REM sleep (like me, I have severe REM-stage sleep apnea). To be clear though, if you're getting restorative sleep and not having any other sleep-related issues, it's unlikely there's any significant problem.
I'm new on cluster science but I've become quite expert on sleep disorders over the past 20 years. Several are mediated in the same area of the brain, involving the same signaling pathways, as are described for cluster patients. I'm not surprised at all that there is overlap and I think as the science progresses we'll find sleep disorder comorbidity is more common among CH patients than not.
Julie