1) Backseat driver/ˌbæk.siːt ˈdraɪ.vər/ is a person who gives unwanted advice or criticism, esp. to the driver of a car.
Origin:
This phrase got its start from the irritating tendency of some people of giving unwanted advice to vehicle drivers. It became popular in the USA in early 20th century, when motor vehicles were introduced and becoming popular.
Example:
In our class assignment group, Matt is acting like a backseat driver. Only unwanted advises and complaints with zero meaningful contribution from him.