My 99 Dodge Intrepid shuts off while im driving, lights stay on though....what could be the problem?

A few weeks ago...i was driving on the street and pressing the gas...then my car just shuts off...so i try to start it again...takes a few times but it does start...so I drive it to the mechanic and they see that the coolant is leaking out so they replace the water pump. Its been running okay for a week but sometimes it would hesitate when I step on the gas. And yesterday, I was on the freeway and it just shut off on me again. I was able to coast on off the freeway down the exit....tried starting it again right away and wouldnt start...waited about 40 minutes then it started. Now when im driving it feels like its hesitating more like its going to turn off again. I had a new battery put in a couple months ago and a new radiator fan....im scared to be driving this thing now