no crank no start intermittent

I have a Laguna 1999 1.8 I have an intermittent problem. I start the car from cold no problem but when I get to my destination the car car wont start, dash light come on but no crank no start not a sound, I have to get a jump start which works 1st time every time. This is an intermittent problem, driving me crazy. Sometimes the car restarts ok, hope you can help.