Intermittant or not you should be able to find the culprit. Take your time in doing so. It might take you several times during several start up cycles.

Disconnect the negative lead from the battery. Use a light tester and jam the point into the negative pole. Clip the other end onto the negative lead you disconnected.
If you are experiencing a short the light will light up.
Disconnect and reconnect one fuse at a time until the light goes out.

If it is intermittant and killing your battery pretty quick Then I want to blame an electrical motor somewhere. Winshield wiper motor for instance.
Maybe an alternator. Those diodes when they do short will cause amp draws.

Put a trickle charge on the battery to keep the charge up. Do disconnect the battery from the negative terminal.

Trickle charge plus time equals a healthy battery. I garantee it!