why wont my car start every time?

hi, i have a 1999/2000 senic megane automatic 1,6v for no reason it just wont turn over. turn it off start again few min,s later and starts ,its getting worse now stalled at traffic lights and threatens to stall at junctions or round about,s iv had aa out twice but its started straight away they even followed me to garage who cant help because it s going help.