OK
I see references to scsi devices naa.6d0946601f70d30022186609290abb0c and naa.6d0946601f70d300228215fee13a5b8c in both the vmkernel.log and in the syslog.log shortly before the restart.
These are the 2 virtual disks created by the dell RAID card on the host and presented to VMWARE as raw storage. Could it be something going on with them? idrac says the virtual disks are healthy. They are what the 2 VMware datastores are built on.
a small portion of the syslog is attached. the reboot happens close to the beginning. right after the 2018-07-26T18:55:02Z log entry