1992 Buick Century No Start/stalls coming to stops

My grandmother just got her car smogged, and passed, but on the way home while coming to a stop, the car stalled out, she was able to restart the vehicle but noticed the car ran rougher. Today the car stalled out once at a stop sign and again turning the corner (decel) to my street. it then wouldn't start. Being a mercedes-benz mechanic, i checked basics, fuses ok, fuel pressure at rail, but found no spark from any coil, i checked the coiil connector for corrosion/broken connection but found none, i began checking for loose connectors/ broken harness, and after wiggling the harness, the car started, and continued to start a dozen times. Thinking it may be a broken wire in the harness i was not able to stall out the car wiggling the harness again. I began thinking it may have just been a coinicidence. Is there a common component that fails that prohibits spark, and is there a test i can do when the ignition goes out again to narrow down the failed component, thanks