Here's one for sleep experts and physicians?!
Question: When I go to bed at night and fall asleep, I wake up constantly and stretch, a whole body stretch, almost like a Yawn for my whole body. What's happening.? this started about a year ago
Answers: When I go to bed at night and fall asleep, I wake up constantly and stretch, a whole body stretch, almost like a Yawn for my whole body. What's happening.? this started about a year ago
What changed about you a year ago? have you put on weight. adopted a new sleeping position, got a new mattress, started sharing yout bed?
If your body is not getting enough oxygen either because your cramped or because you are breathing shallowly or have apnoea it could cause you to stretch and yawn.
If you cannot pinpoint a physical cause it might be woth mentioning to your doctor.