Comment 2 for bug 1584818

This problem occurs because on Ubuntu 16.06 both sssd and autofs are started too early, before network is up. This has been observed in setups with network interfaces configured statically in /etc/network/interfaces (is that your setup as well?) Sssd itself recovers from this condition gracefully, and eventually connects to the LDAP server when network comes up. However autofs gives up after first failed attempt, and must be restarted manually to to properly mount NFS shares.
Please see discussions for bug 1566508 and bug 1588915 (these are separate issues related to system startup that affect autofs, among other things).