My Car turns off on its own

I just bought a 1995 murcery Tracer and I drove it for about 1 hour and the check engine light came on and i got out of the car and looked under the hood wih the car still running and then all of a sudden it shut off on its own...and then i turned it back on and it drove perfectly...but the next time i started it and roled down my drive way and when i got to the bottom it shut off agian but them it started right back up when i turned the key..... i dont know muck about cars so can any one help me?