MacBook is spiraling into a reboot loop

[MacBookReboot]

After a year and a half of no problems, my MacBook has started randomly rebooting itself and spiraling into a reboot cycle. Example: after using my computer for an hour, it will reboot, operate normally for 10 minutes, then randomly reboot again and only operate normally for 5 minutes. The decreasing "normal operating time" will continue until it's rebooting while still displaying the gray boot screen (yikes!) and never successfully fully reboot.

No new software installs (other than system updates - everything current) and when the problem starts I'm only running Word and Safari. At first I thought it might be a heat issue, but I downloaded a temp. monitoring widget, got the CPU temp cranked up, and couldn't replicate the problem.

I took it into the Genius Bar yesterday and had them check it out (didn't find any hardware problems; and they did an archive install). Seemed to fix the problem, but it started again today. Help!

Haven't found any similar posts... much thanks.

 

[silverblack]

I would keep going back to Apple until they fix the problem (I assume it's under warranty). For problem with no obvious solutions, they need to diagnose by trial and error; i.e., starting with simple fixing like reinstalling OS, and work their way in before they consider hardware replacement.

Is there any error log that records the number of times it restarted? I would present those to the Apple.

 

[MacBookReboot]

Thanks - I'm under Extended Care so I can go back for as long as it takes to fix the problem. Exams are around the corner, so hopefully we can get this cleared up by December.

I'll check the logs again when I get back from the office tonight, but neither Genius Bar nor I found any records of the reboots when I went in yesterday.