I've got an iMac running High Sierra, and over the last couple of months it has developed a problem where it spontaneously reboots itself about once a day.
The reboots always occur when the iMac is asleep and the pattern is always the same. When the reboot happens, the startup chime happens twice in close succession. The error message is always like this:
Date/Time: 2017-12-10 08:43:57 -0800 OS Version: Mac OS X 10.13.1 (Build 17B1003) Architecture: x86_64 Report Version: 26 Data Source: Stackshots Event: Sleep Wake Failure Duration: 0.05s Steps: 5 Hardware model: iMac13,2 Active cpus: 4 Time Awake Since Boot: 33000s
I researched Sleep Wake Failure on Ask Different and elsewhere on the web. I tried several things, including:
- Energy Saver: Prevent computer from sleeping automatically when the display is off
- Reset PRAM/NVRAM
- Reset SMC
This iMac is getting a little old and it is quite possible a problem has developed with the hardware, but I do recall this started around the time I installed High Sierra and I've been assuming it's a correctable software problem.
Model info: iMac13,2, BootROM IM131.010F.B00, 4 processors, Intel Core i5, 2.9 GHz, 8 GB, SMC 2.11f14 Graphics: NVIDIA GeForce GTX 660M, NVIDIA GeForce GTX 660M, PCIe, 512 MB RAM 8 GB