In order to start automatically a flash movie, I've used this and in my case it starts automatically:
<object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000">
width="800"
height="200"
id="header_flash"
align="middle">
<param name="movie" value="/Flash.swf">
<!--
<object type="application/x-shockwave-flash">
data="/Flash.swf" width="800" height="200">
>
<param name="movie" value="/Flash.swf">
<!--
<a href="http://www.adobe.com/go/getflash">
<img src="http://www.adobe.com/images/shared/download_buttons/get_flash_player.gif" alt="Get Adobe Flash player">
</img></a>
<!--
</param></object>
<!--
</param></object>
Try it and see if it works or not.
PS: if this is not the solution you are looking for (possibly it will be the case) improve your question with your code snippet.
Good luck!