Are you perchance using STP and not have the switch ports set to portfast?:
You can use 'esxcfg-nas -r' to remount all and/or add this to a script run at start-up.
A common issue appears to be devices trying to mount before DNS is up and thus you can try using IP instead of DNS-name (if applicable).
Thank you TheBobkin, I appreciate your reply.
I have tried "esxcfg-nas -r" but no action has been done, then I have tried to create a script and wrote in it the same command:
esxcli storage nfs add -H <NFS_IP or NFS_HOSTNAME> -s <directory of shared NFS> -v <Volume-Name>
And then added the script directory to /etc/rc.load.d/rc.load
and after rebooting it is mounting successfully but the need to run each VM separately.