$username = ".\Administrator"
$password = "P@ssw0rd!"
$securePassword = ConvertTo-SecureString $password -AsPlainText -Force
$cred = [PSCredential]::new($username, $securePassword)
# または
# $cred = Get-Credential

$vmName = "vm01"

$vm = Get-VM -Name $vmName -ErrorAction Stop
Invoke-Command -VMName $vm.Name -Credential $cred -ScriptBlock { Restart-Computer -Force }
do {
    Start-Sleep -Seconds 1
} until ($vm.Heartbeat -like "NoContact")
Write-Host "$($vm.Name) is Rebooting..."
do {
    Start-Sleep -Seconds 1
} until ($vm.Heartbeat -like "Ok*")
Write-Host "$($vm.Name) is Rebooted."