Car randomly shakes and stalls the code the mechanic cleared was P0299 code?

4 weeks ago, my car sputtered a few times. I stopped and when I got back in and drove a few blocks it sputtered so hard and stalled got it started when to a gas station put fuel injector cleaner in it. For about 2 miles down the road the car engine light came on and went into limp mode. Mechanic replaced Upflow O2 Sensor. Car worked good for 3 days. Then the car sputtered and stalled. It does it over and over again. I have to keep starting it and eventually it gets like this burst of energy and goes fine. I may stop it 2 or 3 times no issue then the 4th time starting it will sputter and stall over and over until again it gets a burst of energy. Check engine light came back on so I took it to my mechanic again. He didn't have time told me to take it to the Chevrolet dealer. Came to pick up the car, it pulled out of parking lot fine then sputter stalled sputter stalled barely then it got power and I drove it to the dealership. Of course, the mechanic cleared the code so there was no engine light or code on the car. Chevy dealership had it for 3 days they said it never acted up for them. I picked it up pulled out of the parking lot went to stop and a light and it sputter stalled over and over finally got it to go pulled back into the chevy parking lot and the mechanic drove it and it never did the sputtering stalling. Took it home. Called another mechanic and made an appointment. I drove about half a mile then I went around a corner and the car sputtered and stalled about 20 times. Black smoke was coming out of the exhaust. Finally got a burst of energy and drove fine to the mechanics. The mechanic said he test drove it a few miles and nothing. It feels like the engine is getting no gas then I don't even have to have foot on gas pedal and then it just shoots forward fast and drives fine until it the next 1, 2 or 3 times I start it then it does the sputtering stalling etc, all over again.