Like you mentioned, it’s absolutely not easy for a lot of people to speak up even when they have great ideas or simply need to clarify. It‘s the personality or the environment that can inhibit people from sharing what they have to say.

In addition to what you said, a small trick that worked for me in the beginning was to shift my mindset by applying inversion mental model — Instead of thinking “what will happen if I speak” I would ask myself “What will happen if I don’t speak”. The latter always guided me to decide when to speak up and when to simply listen.