Born with a silver spoon in one's mouth. Born to luck and wealth. The allusion is to silver spoons given as prizes and at christenings. The lucky man is born with it in his mouth, and needs not stop to earn it.
“One can see, young fellow, that you were born with a silver spoon in your mouth.” —Longman's Magazine, 1886.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894