What does あるとき mean in this sentence?

Question

I came upon the following sentence and its English translation in a collection of parallel short stories in Japanese and English.

あるとき、夜中にふと目が覚める。

Sometimes, just like that, in the dead of night, I wake up.

What confuses me is the translation of あるとき as "sometimes". My dictionary translates あるとき as "once; on one occasion; at one point" which would imply that the sentence describes one occurrence of an event. In contrast, the "sometimes" of the English translation implies multiple occurrences.

Can あるとき refer to multiple occurrences or is the translation somewhat removed from the original sentence?

Answer 1

あるとき、夜中{よなか}にふと目{め}が覚{さ}める。

I'm a Japanese. If Japanese use this phrase, such as in a book as a novelist, the event could occur multiple times, because the phrase is written in a present tense not in a past tense. And, if the phrase is written in a past tense, the event occurred only once.

【An example of multiple times】
あるとき、夜中{よなか}にふと目{め}が覚{さ}める。なぜだろう。理由{りゆう}は分{わ}からないが、少{すく}なくとも彼{かれ}と別{わか}れる前{まえ}にはそんなことはなかった。このところ、こんなこと（＝夜中{よなか}にふと目{め}が覚{さ}めること）が度々{たびたび}ある。

【An example of single time】
あるとき、夜中｛よなか｝にふと目｛め｝が覚｛さ｝めた。頭｛あたま｝の中｛なか｝に何桁｛なんけた｝かの数字｛すうじ｝が残｛のこ｝っている。急｛いそ｝いで書｛か｝き留｛と｝めた。その時｛とき｝の数字｛すうじ｝を今｛いま｝こうして見｛み｝ている。いまだにこの数字｛すうじ｝が何｛なに｝を意味｛いみ｝するのか分｛わ｝からない。

I know the sentence 「頭{あたま}の中{なか}に何桁{なんけた}かの数字{すうじ}が残{の}こっている。」in the example of single time should be written in a past tense in English, but in this context, the sentence is more natural when written in a present tense than in a past tense in Japanese. 　　

Answer 2

As you have gathered, ある時{とき} should only refer to a single time. Sometimes should be 時々{ときどき},　時{とき}には or たまには. The sentence you provide would translate to:

One time, I just happen to wake up in the middle of the night.

This use of （と）ある can be seen elsewhere all in reference to singular entities, such as とある人物{じんぶつ} (a certain person), ある日{ひ} (one day), ある団体{だんたい} (a certain group).

Answer 3

In Japanese, there is no grammatical plural, so this とき can be singular ("one time", "certain time") or plural ("sometimes"). Depending on the overall context, both variants could work here.