along for the ride
Participating but not actively, as in Don't ask me how long this job will take; I'm just along for the ride. This metaphoric term often is preceded by just to emphasize the passive role of the “passenger.” [Mid-1900s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.