What’s the word for: afraid of speaking up your opinion because you’re a new hire and/or a part time employe?

The word, or term, you’re looking for is: “Smart”.

The longer version of the term being: “Smart enough to realize that you probably haven’t been around long enough to know everything that’s going on with the company, and offering your own opinion is very likely to make your supervisors annoyed; possibly to the point of making you no longer having a job.”