Slow first query

I'm running postgresql 8.0 under WindowsXP for a development box (the
production server isn't up yet, and will be linux, so I don't know that
the problem will travel)...

Using a PHP connection to it for a simple web app, if I leave the app
alone for a bit (about 20 seconds I'd say) and do something that
requires a query the next page load is slow, not 20 seconds slow, but
3-5 seconds.... but as long as I stay active the page reloads are
instantaneous.

Is there anything I can do about this, or should I just wait to see how
it performs on my production server before I worry too much?