Could you share the esx boot log?
Just a thought, I remember ESXi hosts presented with RDM luns taking long boot times, check this linked KB if it applies to your environment
https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=10161...
If you found my answers useful please consider marking them as Correct OR Helpful
Regards,
Hussain
https://virtualcubes.wordpress.com/