latex sets images at end of document code example
Example: Start Image from top of page Latex
I assume you issue a \clearpage (or something similar) just before using \begin{figure}...\end{figure}, right? If this is the case, add \mbox{} (or \null) after the figure environment before starting a new \chapter and your alignment should be fixed. Since there's nothing else on the page, LaTeX centres it, since that would be the best way to present the information.