How do I restart SharePoint Timer Service from command line?

SharePoint 2010:

net stop SPTimerV4
net start SPTimerV4

net stop "Windows SharePoint Services Timer"

net start "Windows SharePoint Services Timer"

I realize the OP is requesting a command-line solution, but using PowerShell (run as administrator), restarting the timer service is as easy as running:

restart-service sptimerv4