Hm no, unfortunately the Italian prepositions have a wide range of usages, and the same type of prepositional phrase can be introduced by several of them depending on context. For instance the "complemento di moto a luogo" (i.e. the prepositional phrase related to movement toward a place) can be introduced by (quoting https://it.wikipedia.org/wiki/Complemento_di_moto_a_luogo) in, a, da, tra, su, verso, and per; among those only "verso" is strictly related to movement (or rather direction) and properly translates "toward" (I'm used to consider it an adverb rather than a preposition though).

When you use "sono" you aren't referring to any movement, so in Italian it would be "complemento di stato in luogo"; it can't be "I'm off to the restaurant", but it can colloquially be "I'll be at the restaurant".