Answer:
Hearing something unexpected or touching a live wire can have this effect.
What is in the middle of nowhere?
What occurs four times in every week, twice in every month, only once in a year but never in a day?
In spring I look gay, Covered in a green array, The warmer it gets the more clothing I wear, As the cold grows, I throw away my clothes.
I start in little but I end in full, you'll find me in half and complete.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.