"Windows 7 clients experience a three to five second delay in obtaining an IP address through Dynamic Host Configuration Protocol (DHCP) at restart. This behavior occurs when the clients are DHCP-enabled and domain-joined. This results in Netlogon event ID 5719 and Group Policy event ID 1129. You may experience this issue if the Windows 7 DHCP client is communicating with a Microsoft Windows-based DHCP Server through a non-Microsoft Relay Agent, such as a Layer 3 network switch."
Microsoft has a hotfix for this. You can read more about this and obtain it here: https://bit.ly/rXbwCV