Ideas may occur at any time--a brilliant idea may surprise you while in the shower, during a walk in the forest, or while sleeping. However, your sketching process should not rely on good ideas to randomly appear; you should look for them.
As you organize your exploration better, you will not only get more ideas to explore but also cover the space of possibilities better, reducing the chances of missing interesting ideas.
Design exploration sessions are not like brainstorming exercises. While brainstorming usually involves many people speaking their ideas out loud as they come to mind, a design exploration normally involves participants exploring many possibilities silently in an organized way, for them to be shared with others later.
