wsadmin + jython restart WAS appserver

From wsadmin you may issue a command (using Jython):

AdminControl.invoke(AdminControl.queryNames('WebSphere:*,type=Server,node=%s,process=%s' % ('YourNodeName', 'YourServerName')), 'restart')

works with WAS Base & ND. With ND you have another option:

AdminControl.invoke(AdminControl.queryNames('WebSphere:*,type=Server,node=%s,process=%s' % ('YourNodeName', 'YourServerName')), 'stop')
# now your server is stopped, you can do any cleanup
# and then start the server with NodeAgent
AdminControl.invoke(AdminControl.queryNames('WebSphere:*,type=NodeAgent,node=%s' % 'YourNodeName'), 'launchProcess', ['YourServerName'], ['java.lang.String'])