Learn Romanian: Bunica ne sună din când în când. - Grandma calls us from time to time.

It literally translates to "from when in when", but it is a fixed Romanian expression that means "from time to time" or "occasionally". You can use it as a set phrase in the exact same way you would use the English equivalent.

Is the pronoun ne in the accusative or dative case in this sentence?

It is in the accusative case, meaning it acts as the direct object. The verb a suna (to call) takes a direct object in Romanian, just like in English. While some verbs of communication in Romanian take a dative indirect object (like a telefona), a suna requires the accusative, which is why we use ne here.

Why does the pronoun ne come before the verb sună?

In Romanian, short, unstressed object pronouns like ne (us) must be placed immediately before the conjugated verb. You cannot put it after the verb in a normal present tense statement.

Why is the subject written as bunica rather than just bunică?

In Romanian, the definite article (the word for "the") is attached directly to the end of the noun. The word bunică simply means "a grandma". By adding the -a at the end to make bunica, it becomes "the grandma". Romanian requires this definite article for the subject of a sentence, and it is also the standard way to refer to your own family members, just like capitalizing "Grandma" in English.