Hello and welcome to YorkieTalk!
Cocoa is a cutie and I love his pancake plop! He looks happy and comfy in the pictures you posted.
I have a four month old Yorkie and she does not do the pancake plop but when she sits her bottom will slowly slide away from her front paws and she has to readjust herself. We have hardwood floors throughout the house so unless she is on something (bed, lap, couch, pee pad, etc.) she is constantly trying to sit back up...she may just decide to do a pancake plop like Cocoa one of these days too!