Voyager cuts off when ever you slow down or stop
 

My 2001 Voyager 2.5 crd cuts off very often when I come to a stop or on slow traffic. The problem is more prevalent when the tank level is between 0 and 1/4 and when the engine temperature rises to about 1/3 of the dial ( which is the highest temperature it reaches). Normally I tend to turn off the key and turn it back to accessories and wait about 10 sec before restarting. Can anyone give me a clue as to what to look for in these two cases. The biggest worry is that when it cuts off the power steering is lost and this beast becomes very difficult to control.