Fear of looking dumb has killed more great ideas than actual dumbness ever did.

Most ideas die in the gap between having one and saying it, and what stands in that gap is a picture of how you would look if it landed badly. That picture is almost always worse than the reality. People forget an unremarkable question in about ten minutes.

Next time you hold something back, notice what you are protecting. Then say it anyway and watch what actually happens. Collecting a few of those is how the fear gets smaller.