Looking for some suggestions regarding my 7-month-old son who spends the last 2 hours of his nighttime sleep in a light REM phase. He frequently stiffens his body and arches his back, requiring me to sit up and rock and bounce him so his body relaxes again. On good nights I can do this repeatedly (every 5-10 minutes he requires the bouncing and rocking) until he eventually will go through one more deep sleep and then wake happily for the day. Most days, however, despite...