Do you mean you stopped the server and it rebooted on it's own? If yes that's a hardware problem, I do see some hardware issues logged:
Jun 9 02:27:34 Vault001 kernel: mce: [Hardware Error]: Machine check events logged
Jun 9 02:27:34 Vault001 kernel: [Hardware Error]: Corrected error, no action required.
Jun 9 02:27:34 Vault001 kernel: [Hardware Error]: CPU:0 (17:71:0) MC27_STATUS[-|CE|MiscV|-|-|-|SyndV|-|-|-]: 0x982000000002080b
Jun 9 02:27:34 Vault001 kernel: [Hardware Error]: IPID: 0x0001002e00000500, Syndrome: 0x000000005a020001
Jun 9 02:27:34 Vault001 kernel: [Hardware Error]: Power, Interrupts, etc. Ext. Error Code: 2, Link Error.
Jun 9 02:27:34 Vault001 kernel: [Hardware Error]: cache level: L3/GEN, mem/io: IO, mem-tx: GEN, part-proc: SRC (no timeout)
Looks like they are CPU cache related.