Small drabble, I was thinking of and realizing my theory on why Bella and Edward's hands shocked each other.
It's often said that souls who have known each other in a past life will know when they find one another again. This part of the soul is hidden deep within the recesses of the unconscious mind and can never be accessed by the conscious.
Reunited souls will strike each other witrh sparks in their happyness. The soul recognizes its other half and will be happy.