ShuffleBySong
Shuffles by song for the current playlist. If the player name is supplied, it will be used — otherwise its name will be assumed/elicited.
Invocation options (choose based on grammar-fit):
Alexa, [ open / start / launch ] MediaServer
Alexa, [ ask / tell ] MediaServer [ to / for ] …
{song} can be any of [the] song/tune/track/number/something.
{start} can be any of activate/enable/turn on/trigger.
shuffle again
shuffle things
shuffle playback
shuffle it again
shuffle it up again
shuffle things again
{start} shuffle by {song}
{start} shuffle by {song} in {Player}
{start} shuffle by {song} on {Player}
{start} shuffle by {song} in the {Player}
{start} shuffle by {song} on the {Player}
{start} shuffle by {song} on {Player} player
{start} shuffle by {song} on the {Player} player