Perhaps a personality trait or a group dynamic is making you feel timid. Perhaps you've assumed more than you're qualified to deliver. Or maybe negative feedback has affected your confidence. If you don't, you could lose the job, or worse, complete the job unsatisfactorily and tarnish your reputation. Find a mentor.
Most people are happy, when asked, to meet for a discussion over lunch or coffee.
Identify the traits that lead you to perceive he or she as an expert, and emulate them. Ask for feedback before the client or employer does. The more specific your questions, the more valuable the response. At IVC, we'd rather check in too frequently than not frequently enough. Collaborate with the client to create and agree on the suite of products and services you will provide.