@cs2000
The cron jobs are nice to have, but it looks like watchdog is the one that's helping me out the most, so I'd definitely advise trying that out.
Just Google "watchdog raspberry pi" and you'll find a few tutorials. Instead of using 1 min/24 load, I changed mine to 5 min/70 load.
I've now been mining for about 18 hours with 2 auto reboots thanks to Watchdog.
Great

Ive prepared a USB cable now so il try that first and then the watchdog if not.
It is interesting though as a power issue wouldn't cause high CPU usage which is what your watchdog is rebooting upon... odd indeed.