I found a issue due to Minera 0.3.5 with Raspberry B+ ( New version with 4 USB Ports )
When i power off ( from minera's web page or SSH then poweroff or halt ), after 10 to 15 second, Pi will auto poweron again
How ever, I test 2014-06-20 img form raspberrypi.org, not having this issue, and i manually install minera 0.3.5 and still not having this issue
I can't understand when you have the issue. But probably it's only an RPI config issue (wake up on lan?), nothing to do with Minera.