I've had my cel flashing twice now,and it would run rough. I then shutoff my

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egine and restart. The cel would come as normal and go out. My car would run fine. I took it to a tire shop and they checked it out. They replaced an o2 sensor and new plugs and wires along with a fuel system cleaning. I drove my car and ran errands and no problem until it did it for the second time cel flashes and engine runs rough I restart everything is back to normal. I driven about thirty miles since that happened and my car is running fine what could it be . I can't afford to throw hundreds of $ at it for some shade tree mechanic trys to figure it out.