System reboot seemingly no reason, no logs, only IMPI mentions after reboot

One server reboots every few days seemingly completely randomly. There is no mention in any log of any errors prior to such a reboot. For example, the reboot happens in between these 2 messages from /var/log/messages and journalctl:

Mar 13 11:25:01 server something: some action 
Mar 13 14:33:00 server rsyslogd: [origin software="rsyslogd" swVersion="8.4.2" x-pid="2460" x-info="http://www.rsyslog.com"] start

The only clue I could find is after the reboot, somewhere in the start up it spouts out this IPMI line:

Mar 13 14:33:00 server kernel: [   24.621566] Copyright (C) 2004 MontaVista Software - IPMI Powerdown via sys_reboot.

All the other IPMI and other messages seem to be normal. The motherboard of this server is an Intel S5000PSL. Some outputs from ipmitool:

# ipmitool mc watchdog get
Watchdog Timer Use:     BIOS FRB2 (0x01)
Watchdog Timer Is:      Stopped
Watchdog Timer Actions: Hard Reset (0x01)
Pre-timeout interval:   0 seconds
Timer Expiration Flags: 0x00
Initial Countdown:      0 sec
Present Countdown:      0 sec

Does the IPMI keep other logs that I don't know of and if so, how do I access them?