Listening Ramdomly

My iPod jumps out of the book I'm listening to (even when locked so I know it's not a pocket change) and starts on another.  I can tell I'm listening to a different book, but finding my place in the one I was listening to is somewhat chancy.  Sometimes I just listen to a section over again to get back to my place, but sometimes I know it is previous to where I was but is something I didn't hear.  So it is an advantage somewhat that I'm familiar with the story.  If it is a totally new book, I can't tell if it's skipping around with the characters' parts of the plot or if the book just doesn't make any sense.