Hello Marco,
Intrastat relevance is dependent on country and each country generally has its own norms.
In general, when there is a 'physical' goods movement between 2 EU countries then the shipments become Intrastat revelant.
In some countries even shipments to private accounts (having no VAT no.) have to be declared.
These transactions are identified by specific Nature of Transaction codes which help statistical authorities in Identifying that these are sale to a private individual.
Regards,
Kavitha.