how can i find this fault ford fiesta eco climate 55 plate ?

i have a fiesta and every now and then the engine would turn over then stop for a brief sec then continue to start i was told this was a dead cell in my batt which i have changed the fault seemed to have dissappeared for as while then the other day i came to the car i turned the key nothing not no dash boared lights not eneything then i switched off back on again and everything worked but my first problem has come back please help