What about when a verb means the same thing when it's transitive and when it's pronomial?
Mover - to move. Moverse - to move.
"No te muevas!". Don't move.
Why couldn't you say "no muevas!". Does it matter which way you say it? thanks.
In English we don't typically say "to move oneself", but that's what "moverse" actually means. "No te muevas" - don't move (yourself). On the other hand, "mover" is to move something else. "No muevas ese papel" - don't move that paper.
If you will notice that all of the examples under pronominal in the dictionary (for moverse) are intransitive. This has a lot to do with the detransitizing se that Lazarus used to refer to. When a Spanish speaker hears mover (non-pronominal, transitive) he thinks (move what?) To allow for intransitive uses Spanish uses the se (move itself) to answer the what without actually having a direct object.
No se muevan. Don't move. (intransitive)
I think Lzarus' best explanation utilized "the ship sinks. (is sinking)
non- pronominal or transitive- the ship sinks what. The ship sinks (e.g. another boat.) El barco hunde...¿qué?
pronominal or intransitive. -the ship sinks itself. El barco se hunde. Therefore, the se is used to detransitize the transitive verb hundir.
I don't like to think of these verbs as reflexive, however, because when you think of it as the boat sinks itself and it appears that there is a d.o. and that the sentence is transitive which it is not. They also are easily confused with passive se (the boat was sunk), but passive voice require an agent...the boat was sunk by pirates so it is not passive either.
So, to get back to the original question, you cannot say
No muevas because you are using the transitve (mover) and not providing a what to move. You must use the detransitizing se to say No se muevas intransitive.