@law59
I noticed this also, particularly after Breakfast, and I reasoned that it takes energy to digest food.
So, I have been practicing (non-physical) yoga nidra (via free YouTube channel of Ally Boothroyd) after I eat and before I take my shower.
My 'favorite' is the "17 Minute Yoga Nidra Nervous System Reset". It doesn't take long and really does energize me. I'm always amazed.
Good luck,
My best,
Pam