back-seat driver 
noun informal
1A passenger in a car who gives the driver unwanted advice.I would need a sound proof partition for my passengers, though - I can't stand back seat drivers....
- I can't stand back-seat drivers… even worse, passenger-seat drivers.
1.1A person who is eager to give advice about something for which they are not responsible.‘I'll be in the driving seat because it's the only seat to be in,’ he answered a conference delegate who pointedly asked what the candidates thought of back-seat drivers....
- She failed to appreciate that the term ‘back-seat driver’, in most people's eyes, was pejorative: she thought it merely indicated helpfulness, whereas others saw it as meddling and controlling.
- After all, remember how he once described critics as back-seat drivers facing the wrong way, and certainly critics are usually pretty good on the past, moderately good on the present, and helpless and hopeless for the future.
Derivatives
back-seat driving
- Whatever assessment one makes of the term of a leader who has enjoyed a long and mostly undisturbed innings, it is less easy to forgive back-seat driving designed to sabotage his or her successor.
- How many of us love back-seat driving, even when we love the people who're doing it more than life itself?
- But back-seat drivers and back-seat driving are variations of the same expression.
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