Did i hurt my ignition coil?

I drive a 1998 Infiniti I30 and I slowly drove off a curb the other day and my car was fine afterward. All that afternoon if was fine and the next morning too. But the next day around 12:00, I got in it and it was shaking very hard. It scared me. It shook when I was idling and when i changed gears. I took it to my mechanic and he said it is the Left Ignition Coil. I asked what causes that to go bad he said it just usually happens to people from time to time. I'm wondering did this just randomly happen as he said, or when I bounced the curb, did it happen. If so, why did I get a delayed reaction because the car was fine the day it happened and the beginning of the next day.