Get-Update.ps1

$Session    = New-Object -ComObject 'Microsoft.Update.Session'
 
$Searcher   = $Session.CreateUpdateSearcher()
$Query      = 'IsInstalled = 0 or
               IsInstalled = 0 and DeploymentAction = ''OptionalInstallation'''
$Search     = $Searcher.Search( $Query )

If
(
    $Search.Updates.Count
)
{
    $Downloader = $Session.CreateUpdateDownloader() 
    $Downloader.Updates = $Search.Updates
    $Download   = $Downloader.Download()

    $Installer  = $Session.CreateUpdateInstaller()
    $Installer.Updates = $Search.Updates
    $Install    = $Installer.Install()

    If
    (
        $Install.RebootRequired
    )
    {
        Restart-Computer -Confirm
    }
}