Shoulder-shrugging tics are motor tics, and usually involve moving the shoulder in an up and down motion. This may involve one shoulder or both, and movements may have a specific pattern.
The CDC lists shoulder shrugging as an example of motor tics, showing how common this tic is in tic-disorders.
Being misread by others
Shoulder shrugging (outside of tics) is commonly used to display a feeling of uncertainty, or ‘I don’t know’.
Mistaking a tic to mean this is highly unlikely, especially as tics often seem ‘random’ or untimely from an outsiders perspective.
Shoulder shrugging can be very tiring, as motor tics use muscles. The frequency and severity may cause aches and pains in the region, with a risk of injury for more severe shoulder tics.