I have watched Young Sheldon up to the latest episode, whenever the theme song is played, Sheldon is shown moving away from the cow. Why is it like that?
I think it is just to throw Sheldon off. He is well known to be germophobic, and have some pretty irrational fears...so the cow ruining his perfect shot and then even stepping toward him is to give the audience a smile as he uncomfortabley steps back to put slightly more distance between him and the cow
I am guessing you are talking about the end of this sequence:
At the end the family is obviously posing in a similar fashion to a monument of great american heroes. The background also would be quite suitable to the western genre. So two soft connections to the founding days of a almost constantly great nation.
The protagonists look up, slightly to the side and are motionless like statues. They are disconnected from the viewer, clearly aspiring to something great.
Then they all turn their head, which is quite uncommon for statues, let alone monuments. So they already get their first crack.
Then the camera pans and shows an ordinary cow standing right next to them. Ruining the perfect wild-west-monumental-panorama.
Then the cow even dares to take a step towards them.
The mighty, aspiring statues back off, but only a tiny, marginal bit.
Then they resume their monumental positions again. Once more magnificent, just with a cow next to them.
Addition: Some of my example statues are of the dark chapters of American history. I am not sure if there is really a pattern there. But possibly it could also be a common trait of redneck-ish statues to be disconnected from the common folk in front of them.