Feeling unwell (меня тошнит)

The Body Reports, You Suffer

Russian has a family of verbs where no one does anything — a state simply hits you. The person it hits stands in the Accusative, the verb stays frozen in the third-person singular, and there is no subject at all:

Меня *тошнит. — I feel sick (literally: [it] nauseates me). Сестру укачивает в машине.* — My sister gets carsick.

Accusative, Not Dative

You already know the dative states — мне не спится (I can't sleep), мне холодно. This family is different: the experiencer is a direct target, so the case is Accusative. Compare:

Мне плохо. — dative: I feel bad. Меня тошнит. — accusative: I feel sick.

The two frames live side by side, and the verb decides which one you need.

Past and Aspect

In the past the frozen verb turns neuter: Меня тошнило всю дорогу. — I felt sick the whole way. The state is ongoing, so the imperfective does the work.