Reflexive verbs help please

Reflexive verbs help please
 

Are reflexive verbs only used for yourself/your own attributes? (ex: hair)

Me lavo la espalda.
Me cepillo las dientes

Or is it also for possessions aswell since they belong to me, such as a car?

I was playing an online video game which involves cars and somebody said
"Se compra auto Volkswagen"

I'm guessing that translates to: Buy yourself a Volkswagen car
He doesn't need an en for a preposition in between compra and auto like you would in English?

me comprare coche mañana noche.
Is that correct? I will buy myself a car tomorrow night.

Thanks for any help everyone, reflexive verbs are strange for me since they don't really exist in English. Object/Indirect objects also make zero sense to me at the moment too lol.

Reflexive verbs are only used to reflect back on the subject, yes.
The other case you mentioned is not a reflexive use.

Pronominal verbs are the verbs whose infinitive form ends in -se. Reflexive verbs are pronominal verbs, but they aren't the only pronominal verbs.

I believe you meant 'un' instead of 'en' when you asked the question about placing a preposition before 'auto'. Actually, 'un' is needed, but it isn't a preposition. It's an article. In particular, it's the indefinite article and translates as 'a' or 'an' in English.

Me compraré un carro/coche/auto mañana por la noche.
I will buy myself a car tomorrow night. (The car is for me.)

Compraré un carro mañana por la noche.
I'll buy a car tomorrow night. (It may be for me or it may be for someone else; this isn't known without more context.)

Se compra un auto Volkswagen. = He/She is buying a Volkswagen car. | You are buying a Volkswagen car.
The pronominal verb in this sentence is conjugated in the present tense, not the imperative mood ('buy yourself a car' is a command and it has a very different conjugation). Note that I didn't call the verb a reflexive verb. This is because it is a pronominal verb. That simply means that the verb has a pronoun.

There are many more things that can be said about pronominal verbs. Have a look at this thread to see if it helps any.