Gray globe (earth) appears after restart for no apparent reason - might something be wrong? I restart my MacBook Air OSX 10.8.5 every few days as a routine habit. Twice in the last few months it has come back with the globe (earth) image displayed for 20-30 seconds (I believe it was flashing), then continues on to start normally. See sequence of images.

The first time was immediately after removing some software which displayed my screen via WiFi to a projector at a company (downloaded earlier from the projector mfr. website). Second time nothing particular except that I only had 3GB of remaining disk space at the time.

Should my computer/OS ever display the globe image spontaneously? Is this something that "just happens" sometimes, or should I be looking for a cause?
This means your mac is trying start up using files on your network instead of the copy of mac os on the hard drive which there is none so your mac is stuck in a temporary loop. when its done it gives up and boots from local files on the hard drive. Try turning on airplane mode before the restart to prevent the globe from showing up.