C.G.
My niece wakes up shaky, and when she was little we were all concerned. In her case, the shakes were when she FIRST woke up. She'd come down the hall rubbing her eyes and shaking. It was scary. She'd come sit on your lap and her little hands were so jittery. After she was fully awake (about 10-15 min.) she was fine. The doctors said not to worry about it, unless there were other symptoms, since it only happened when she first woke up, and it stopped on its own.
I would be concerned about hypoglycemia if the shaking stops only when you feed him.
Since I am not a medical expert, you may want to question your pediatrician, because as we all know each child is different.
I just wanted you to know that some kids just wake up shaky. My niece is almost 10 and still does this, but neither of her sisters do.
Blessings,
C.