Unusual stalling

Hello, I have a 2007 Saturn outlook. The same night I purchased it used, it stalled going down the road. No crank, no sound. Lights etc all worked fine. Jiggled crank relay and it started right up. Replaced crank relay, and drove home. The next day, it stalled again going down the highway. There is a clicking sound and it started almost jerking, trying to stay running. The check engine and pass side airbag lights flickered in tune to the clicking sound. Finally stalled all the way and pulled over. Would not start, turned key all the way off and on, and it started again. Has done the is probably 50m times since. We have replaced crank relay, pcv valve, air filter. No check engine light. Sometimes when it stalls, it will start right back up, but sometimes, no click no sound. Tap on relays under hood with a screwdriver, and it will sometimes start again. Please help!