Nightmares only while sleeping on left side

For 5 years now, I have violent nightmares when I accidently fall sleep on my left side (because it is so bad, I try to always sleep on my right side). While sleeping on my right side, I either have no remembered dreams or I remember pleasant dreams --- no nightmares whatsoever on my right side.

I am a 60 year old female. Blood panel normal. No C reactive problem,  205 LDL, 78HDL.  Triglicerides (triglycerides) (I remember that they were slightly elevated.) No other problems that I know of except slight skeletal scoliosis and spondolesthesis. (from an L4-L5 laminectomy and fusion 20 years ago.

Heart? Nuero? Skeletal?

Thanks, Barb