Q: Underneath truck

A strategy is to have a "knowledgeable" assistant with you so that he or she can be outside the vehicle right at the site of the suspected noise when you get in. If that person listens very carefully, he or she would hopefully pin down the location. The "crack" type noise just represents sudden movement, likely in a suspension part. It apparently is happening after the vehicle "settles" and that is why you only hear it initially. Once the suspension moves, it leaves that "settled" position at which obviously something is binding. An alternative is an inspection as there could be telltale signs of wear, or damage, that will be visible to a mechanic. The recommended service to request is a suspension noise diagnostic.