Car now being weird

Car is a 2012 Hyundai Sonata gls 2.4L

I changed my engine and cabin filters a day or two apart, the second I changed the engines filter and drove home I kept having acceleration issues that weren’t there with the old one. My car now randomly decelerates despite having being on the gas the whole time and not letting up one bit, it slows down to a normal crawl all cars do and no matter how much more I press it will not give any until I step off the gas and press again. No codes showing up that pertain directly to this either and nothing like this really happened prior to changing it, the closest I could say was inconsistency with accelerating where I suspected either throttle body needed to be cleaned/changed or the filter itself being dirty (it was yellow).

The mechanic I brought this to only got to check on it minimally and left me with “I don’t see anything, it’ll have to get worse for me to fully check it out to see what’s wrong easier”, so would anyone here be able to give me their educated guesses cause I’m half lost on wtf happened

Edit: so I just got off work, parked at my usual spot and saw my tail lights were still on despite every other light being off. I fiddled the brake and they turned off, so with this in mind I fiddled the brake whenever my car would decelerate when driving and almost every time that I can recall doing it would this make my car accelerate like usual without taking my foot off the gas and pressing again.