If you don't rest yourself, what do you rest? I don't agree that rest can't be used as a reflexive verb in English, even if it's usually encountered as a stress on the subject. Considering you can rest your horse and your legs after long exertion, resting yourself can't be said to be wrong.
Whilst it might not be technically incorrect it's a collocation which is basically never used. If someone said "I'm going home to rest myself" you'd know what they meant but it'd sound weird. "I'm going home to get some rest" is a much more common and natural sounding collocation.
I won't tell anyone it shouldn't sound weird to them, and I hope in return others might accept it doesn't sound weird to others. I hear it all the time and have lived all over Scotland and the North of England. It's absolutely a thing.
"What did you do at the weekend?" "I rested myself."
In present tense, the reflexive verb may sound a little odd because deliberately speaking in that manner can sound a little self-important. Or pompous/overly-elaborate if the reflexive noun is for a second or third party. But it's correct English and utilised widely in literature and other writing. When faced with the Italian reflexive pronoun/verb, it's not only a correct translation but probably the most technically correct and possibly even the closest translation in terms of tone. The use of clitics in Italian is often a measure of a speaker's sophistication in the language, and the composition "I rest myself" is sophisticated in English too, the difference being that English tends to keep its sophistication to formal, written language these days.
If we wanted the closest translation of "I rest" in Italian, "risposo" would, in my opinion, be closest. But Duolingo's Italian course is generally poor at picking up nuances in English, tending to squeeze all the subtleties of Italian into a handful of expressions. It's not that Italian has a half dozen ways of saying the same thing, it's that Duolingo is failing to use the breadth of English appropriately.
But "burn" isn't a reflexive verb in English, yet "ti bruci" was translated as "burn yourself." So I am really confused. And frustrated. I thought I learned form "ti bruci" and put in "rest myself," but I got it wrong. So I can't win.
How are we to know when Duolingo wants us to translate it to "yourself" and when it doesn't?
Resto also means "I stay" or "I remain" (also remainder/change as noun) e.g. Resto qui = I'll stay here
Riposo is can mean "I rest/sleep" or as a noun "rest/relax/sleep".
Since it's a noun you can use it to say "at ease / relax". So: "mi riposo" makes it clear your talking about yourself, but I think "riposo" is also valid for this case.
Riposo tutto il giorno = "I rest all day". So you don't always need the "mi" but it would make it clearer.
There is a bit of cross over between resto and riposo in that they both can mean "rest" in different senses in english.
I think resto is more towards "remain/stay" and riposo more towards "resting/break/retirement".
I don't think there's a hard and true rule here. When you are doing something to yourself, there is usually a pronoun: I rest (myself) - mi riposo I get (myself) up - mi also I sit (myself) down - mi assido
But I am sure there are exceptions. The simplest trick is to buy an italian verbs app and check there if the infinite version of the verb finishes in -si :)
From wikipedia: "In grammar, a reflexive verb is, loosely, a verb whose direct object is the same as its subject, for example, "I wash myself". " So the verb being reflexive means that it goes together with a reflexive pronoun like myself, ourselves, etc.
The sentence "I rest myself" could alo be translated as "io mi riposo", the reflexive pronoun "mi" basically means "myself". "Yourself" (single person) is translated as "ti", etc.
The fact that you can leave out personal pronouns (I, he, she etc.) in Italian can make it a bit confusing!