Hi Emmanuel,
As suggested, I checked to the ESXi host by directly connecting using vSphere and there is not "Hardware Status" tab but when I checked in the "Tasks & Events" tabs. I didn't found any events with "Host IPMI system Event Log", which is observed while connecting to the vCenter using vSphere client.
secondly, I connected to the iLO of the ESXI host and the health status observed is Green. So seems there is no issue on the ESXi hosts. but would like to know the reason for the alerts appearing on the ESXi host continuously, when I connect to the vCenter Server.
regards
VK