Radio/tape Cd Player problems of the 2006 Dodge Grand Caravan

For no apparent reason, the engine shuts off while driving. The clock remains on, but accessories such as the heater also shut off, and I have no power assist with steering. So far, it's happened within 5 minutes of start-up; the outside temperatures were below freezing, but the engine has not always been cold. 1/17/07 approx. 5 min. After I'd been driving, at about 30mph, I realized the noisy fan for the heater turned off. I thought maybe the new van has a feature I didn't know about, where it reaches a set temperature then shuts off automatically? then I realized the radio had also gone quiet. I tried to accelerate but it wasn't responding, so I went to pull off on the shoulder and discovered I didn't have power steering, either. Fortunately, I was able to brake. I turned the key to the off position, restarted the van, and it seemed to work fine. At no time did I see a check engine light. 1/18/07 I had driven to a gas station, turned the van off to fill the tank, and restarted it a few minutes later, to drive away. I accelerated about 5 feet before the van turned itself off again. I stopped, moved the key to the off position, restarted it, and went on my way. 1/24/07 I backed out of the garage, but after I accelerated in reverse, about 10 ft. Down the driveway the van turned itself off again. Other days I had the heater/accessories running, but this time nothing else was turned on. The clock remained lit, so it doesn't seem like a battery issue. I turned the key to the off position and restarted the van, resumed my drive, and made an appointment with the Dodge dealership under warranty. They said there were no computer codes showing; they drove 17 mi. But couldn't duplicate the problem. Since then, the van has only shut off by itself once more when my spouse was driving, but now it seems like a probable ignition switch safety issue to investigate.