1999 Chrysler Grand Voyager help

Hi there,
i have a 1999 2.5 td le
well the car cuts out alot, some times when you brake, sometimes when just just driving along.
if you turn key off reset car it starts again fine, until it cuts out again, so you just reset, and off you go again, also it drains the battrey if you dont use the car for 2, 3 days. Please can you help me
many thanks
paul
i have 5 kids, so need a safe car