1998 Mazda Protege car revving

for the past month or so my car has been revving when i am waiting for a light...it is like i am pressing on the gas but i am not ....the car has gotten worse over the past few days it does it(revs up) almost every time i am waiting for a light to change...last night the car turned off but i was able to restart it....

i have owned the car for a lil over 2 years and the engine light always would come on after buying gas but eventually would go off...for weeks the engine light has consistently remained on

can you please help me understand the problem
what can it possibly be?

thanks for your help