There's no such thing as a stupid question. There may be stupid timing for it, such as a student asking when an exam is 5 minutes after the teacher already announced that information. But that was still a good question, they just asked it at a horrible time.
In general, there are not too many restrictions on asking questions. It's a lot about timing them. For example, you don't want to ask too many specific questions about implementation details if you're still trying to find out what a client needs in a potential product. Their needs are probably going to change every time you talk to them at this point and planning the implementation too rigorously could be a waste of time.
So, what are the benefits of breaking out of your fear of asking questions and just doing it?
To an extent, who cares how they feel about you asking a bunch of questions? Your career is yours and only you can be responsible for taking it to the next level.
I can't tell you how many people I've met through the DEV Community site and Twitter over this past month. It's really exciting how much support you can find in this industry if you put yourself out there.
Sometimes the scariest part about asking questions is knowing how to ask them. You can make 10 attempts at Googling something and Google isn't going to judge you for doing it. Re-wording a question to a human a few times to make sure you're getting the right information? That can potentially be frustrating for both of you. But good news! The more you ask questions, the better you get at wording them.
Have any insight on questions that you'd like to share? Leave a comment or send me a tweet! :)