Random reboot - is there a way to know why ?
When pfsense reboot randomly, is there a way to check what happened without a syslog ? any crash info ?
Sounds like it may be a kernel panic. You could install a developer kernel and then instead of rebooting when it hits a panic, it will stop. You can then look at the console and see what the error is, get a backtrace ("bt" at the debug prompt) and then post them here for us to look over. Even if you don't have a serial console, a picture of the screen will work. Even a cell phone picture will be OK as long as it is legible.