As stated you have a very strong family history of Coronary artery disease.Which likely puts you at risk of blocking of arterial circulation in any other part of body but the most likely situation you are worried about is called as Peripheral neuropathy
. This explains that the nerves are being damaged commonly due to Diabetes
or Vitamin deficiency
.Once the nerves are weak a minimal stretch like a constant posture for long time in sleeping and Sitting will produce the sleepy sensation.Please consult your general physician for B-12 assay and blood glucose
levels and Lipid profile
.You can start on the B-12 supplement even before any diagnosis. Hope this helped. Feel free for any further quarries.