The speaker is jetlagged, caught between sleep and waking in a body that hasn't caught up with the clock. The opening lines, "long ear / long eye," turn the speaker into something like an animal on alert, all senses stretched out in the dark. Being awake for "an hour" suggests a night broken into odd pieces, with no clear sense of when it begins or ends.
The second stanza gives up any sense of control. The speaker dozes "of necessity" and wakes "for the same" reason, as if neither sleep nor wakefulness is a choice. Then comes "grace of God," which can be read two ways: as a gentle, almost grateful acknowledgment that rest and waking are gifts, or as a wry shrug, since nothing else could explain this rhythm. The poem's mood is quiet, drowsy and a little humble. It captures the odd stillness of being awake when the world isn't, and finding a kind of peace in simply being carried along.