1998 Plymouth Voyager starting issue

My 98 grand voyager expresso with a 3.3 motor has a starting problem. About once a week I try to start it and it will start as normal, but then die immediately. When I turn the key again, the starter cranks but engine doen't start. When I turn the key again, nothing happens. After letting the van sit for several hours it starts as normal. Was told over the phone by a chrysler mechanic that it was possibly a bad alarm sensor in one of the doors. Any suggestions?