Myoclonus describes a symptom and not a diagnosis of a disease. In its simplest form, myoclonus consists of a muscle twitch followed by relaxation. A hiccup is an example of this type of myoclonus. Other familiar examples of myoclonus are the jerks or "sleep starts" that some people experience while drifting off to sleep. These simple forms of myoclonus occur in normal, healthy persons and cause no difficulties.
80 % of the populations experience myoclonus "jerks" when sleeping or just falling asleep.
I experienced hypnic jerks way before I was dx with GERD.
Perhaps checking with your Dr. re GERD or anxiety as a contributing factor to your hypnic jerks.
Be well and hope things get better for you