If writing that a character is shrugging – which is useful when showing he is uncertain or indifferent, depending on the situation – there’s no need to say he is shrugging his shoulders. That would be redundant as shrugging by definition is to raise one’s shoulder’s slightly.

It’s sort of like writing, “I’ll meet you at 9 a.m. in the morning.” There’s no need to add “in the morning” as “a.m.” by definition is “morning.”

To wit:
WRONG: When asked when the plane from Los Angeles would arrive, Emma shrugged her shoulders.
RIGHT: When asked about taking their honeymoon in New York City, Olivia shrugged.