How do i fix my ford, mondeo?

When in traffic, my 1998, 1800cc Ford Mondeo, turbo diesel car revs up to about 4000 rpm for no reason for about 3 seconds, the diesel tank always has to be more the 1/4 full or the car is liable to cut out and in the mornings when i start the car it might start up and then stop and when i go to start it again it takes a few seconds for it to get going again. How do i prevent all these things from happening Thanks