new to forum need help

Hello everyone im lonewolf 6.7 im new to this forum but have been following it for quite awhile and have enjoyed following as a guest. I have enjoyed all of the information I have gotten from here and am hoping someone can help with a problem I am having with my truck that nobody at the shops I have taken it to can seem to figure out. I have a 2007 Volvo 630 and for some reason it just quits running with complete power shut down then refires and goes again. I am thinking a bad wire somewhere but cant find it shops say they have checked all wires in harness. I have even replaced the ECM to try and fix but still doing same thing. When event happens I cant even turn on flashers to let others know im having a problem its like battery cables have been disconnected. Any help would be greatly appreciated and thank you in advance.