Learn Hardcore Latin: Frater autem sero surgit, quia nocte non bene dormivit. - The brother, however, gets up late, because he did not sleep well at night.

Because autem is usually postpositive in Latin. That means it normally comes second in its clause, not first. So Frater autem... is the expected order.

It often means however, but, or on the other hand.

Is autem the same as sed?

Not exactly.

sed is the more direct, stronger word for but
autem is often a little softer, more like however or meanwhile

So autem often links the sentence to something previous with a mild contrast.

Why is there no word for he before surgit?

Latin often leaves out subject pronouns when they are not needed. The verb ending already tells you the person and number.

surgit = he/she/it gets up, rises, or is getting up
dormivit = he/she/it slept or has slept

Since frater is already there as the subject, adding is (he) would be unnecessary.