Had I not been awake I would have missed it,
A wind that rose and whirled until the roof
Pattered with quick leaves off the sycamore
And got me up, the whole of me a-patter,
Alive and ticking like an electric fence:
Had I not been awake I would have missed it
It came and went too unexpectedly
And almost it seemed dangerously,
The choice of words adds to the vitality of the poem, with percussive,  plosive  “t"s in "ticking” and “electric”. 
 The speaker feels alive with electric charge, and reinforces this with unpredictable spurts of meaning, such as conveyed in stanza two.
Had I not been awake I would have missed it