NHTSA Complaint #11457530 — 2016 HYUNDAI ELANTRA

So back in November of 2020 I had a few instances where my car had issues shifting into a different gear while I pressed the gas. It was like it stalled and was suspended for a moment making a really weird noise and then got punched into the next gear super fast and made a bad noise. I was driving between 20-35 miles when these occurrences happened. I went to the Hyundai dealership and had them look at my car but they found nothing. The mechanic test drove it but they found nothing was wrong. The attendant made notes on my account about all of this so that there would be a record. He told me to come in again if I had any more issues like this. Fast forward to now March 19th 2022, there were 4 occurrences in one day, where my car felt like it was stalling differently. While I was pressing the gas pedal driving between 20- 30 miles when suddenly it felt like there was a delay like liquid trying to pass through a tube but bubbles of air were blocking it from getting the liquid to flow. Which made my car shake and feel like I was driving over a bumpy road. I feel like if there had been cars in front of me for the first few instances, I could have rear-ended them. Luckily, that was not the case. Now, for the other occurrences on March 19th, 2022 if a car would have been going faster behind me, they could have rear-ended me, especially because of the stalling in acceleration. I've made an appointment with the dealership for the end of this week but I am rrying to go in as soon as possible to get this looked at. I think its either a transmission, engine, or fuel system error just for the simple fact of pressing the gas and feeling it stall and have to force itself into a different gear.