Check engine light goes on when I start with my key but not with remote start.

What is your question?

So I bought this used car and I test drove it for about 15 minutes and the check engine light was never on. Then I came back and purchased the car and as I was driving home I noticed the check engine light was on. And when I got home I tried remote starting my car but it wouldn’t work because the check engine light was on and it has been on for a couple days. Then just today the check engine light was still on and I wanted to see if my remote start would work and it did! And then I put the key in the ignition and the check engine light was off. Then I turned the car off and put the keys back in and started it up again and the check engine light was on again. And it repeats. I can start up the car with remote start and the check engine light goes off but when I start with the key in the ignition the light comes on. What might be causing this?