He was alone on the bus, dozing off.

车上只有他一个人，这会儿在打盹。

He was alone in the bus, dozing off.

车上只有他一个人，这会儿正打着盹呢。

You're dozing off again!

你又在打瞌睡了！

I often catch him dozing off in class.

我经常发现他在课上打瞌睡。