Hello, I'm completely new here so I apologize ahead of time for any naivety.
That being said, I'm also a new car owner.

2 months ago I bought a 2003 2.4L 4 cylinder automatic Eclipse GS from Autonation. The day my warranty ended was the day my car started doing something funky. I'm not at all car literate, so I'm clueless as to what's going on, and my father isn't familiar enough with Mitsubishi cars to have a sure idea yet.
My car has about 103k miles on it, haven't driven it hard once, and is very well taken care of. This last Thursday, I drove it to get some lunch from my work, not even a mile, and as soon as I hit around 40mph, it was like it went into neutral. I tried to accelerate and I got no response. So in a mild panic, I continued to press on and off the pedal, and it eventually responded and it was fine. it did it 3 more times on this 2 mile trip, however on the way home a few hours it was perfect. Yesterday (sunday) it did it to me again, however at around 20mph. It did it about 3-5 times before it suddenly was fine again. My boyfriend tried shifting the car around manually to see if that would help, however during shifting into 2nd and 3rd gear it immediately did it to him, but not later on. He said something about it reacting around 4000rpm.

I went to Autozone to see if any codes were coming up; none. They tried multiple readers. The only suggestion I was given was to check tranny fluid which is right where it's supposed to be. My car hasn't shown any struggle before this, it's very out of the blue. I just need an idea of what might be causing the problem and what parts I need to be looking at... I think it may be some sort of sensor, however my father thinks it might be the shifter itself. Anyone have any ideas??
Thank you. I appreciate it.