I have similar thoughts myself at times, though mine tend to be more related to what something would feel like, such as "I wonder what it would feel like to be hit by that car?"
Also, not to assume on anyone here's intelligence or lack thereof, but I've found that in general people who are more intelligent or creative, especially those that are both, tend to suffer more from these thoughts. It's because while the average person who is jogging down the street may be thinking something like "it's hot out here", more intelligent and creative people tend to be thinking about several things at the same time and their brain makes the jumps to new things much easier. As such it becomes much easier for a stray thought or stimulus to set you on the path of "what would it be like if I did this?" and then your imagination kicks in to flesh out the details, making the thought much stronger. Of course this is no hard and fast rule, as I know several intelligent/creative people who don't think these thoughts, and several not-so-intelligent/creative that do, but it is a tendency that I've discovered.