Good questions are at the heart of good inquiry. They should be higher-order, rich, worthy, essential and/or fertile. They are often open-ended (have no right or wrong answer) but are backed by subsidiary questions which are usually closed. Get the initial question right and the rest of the inquiry flows well.
Young children and those new to inquiry will need help in framing the initial question or problem. The ultimate aim is for them to be able to frame their own questions for inquiry but initially they will need teacher guidance to do this.