So I was driving home the other day and out of nowhere my check engine light turned on, I couldn't be bothered with it because that happened before and it turned off so i assumed it would happen again. Well it didn't turn off and now my car is feeling very unresponsive. When i press on the gas the car stay at around 3,000 rpm and it doesn't go higher until I manually shift using the semi automatic transmission, and then when i come to a stop the car starts shaking a bit mainly in the drivers seat. I also noticed a small gasoline smell but I was unsure if it was my car due to being in traffic (windows were down) so I would just like anyone's opinion on what is wrong so I don't take it to a shop and get charged for something that is completely irrelevant to the problem.
Car is a 2002 c240 at 84k miles

Thank You,
Dino

 

Get hold of an OBDII scanner & scan for codes. Stops a lot of guessing.

 

What Glyn said.
Get an OBD-2 code reader (or borrow one from Autozone for free) and post the codes here.