What could this be ?

My car started doing this today. I drove it yesterday and it was fine. Whilst i was driving it felt like it was slowing down and then i would put my foot on the accelerator and it would sort of jolt forward. I turned it off and turned it back on and it wouldn’t come back on and i tried it a few times then it came back on but straight away turned off on its own. I turned it off and left it for 20 mins then checked my oil, oil level seems to be fine, so i turned it back on and it seemed fine then drove it and it seemed fine but what could this be?