If I shift wrong, they freeze on one side.

Are you referring to this?

Scientists believe this ensures even and steady temperature, maintaining the internal shell membrane, and also proper distribution of nutrients.

If you've ever seen a bird nudge its eggs with its beak, you may have wondered what all the fuss is about. Turns out, the behavior is a critical part of incubation, and each species may have its own egg-turning recipe to hatch a healthy chick, a new study shows.

Scientists believe that most birds rotate their eggs to ensure that the embryo gets enough albumen—the mixture of water and protein that makes up the "egg white" part of an embryo and provides nutrients to the developing chick. Too little albumen leads to an underdeveloped and usually sickly chick, research on domesticated birds shows. Few studies have investigated egg turning in wild birds, in no small part because the adults are, naturally, in the way.

To get an unprecedented look at what's happening in the nest, Shaffer tricked seabirds into treating plastic eggs with sensors hidden inside as the real thing. Researchers have previously slipped artificial eggs outfitted with sensors into the nests of unsuspecting birds, but Shaffer's team is the first to capture "a full turning" of an egg. That's because the loggers record 3D orientation (thanks to a combination of three-axis accelerometers and magnetometers), as well as temperature.

Short Article Here

Nesting and hatching are much more complex and problematic than most media portrays them. I did a post on hatching before, and it takes about 24 hours from when the shell pips (first crack through to the outside) to when the bird is free from the shell. That's a lot of physical exertion to expect of a newborn! (Here's a second hatching post I found.)