hello, this is my first post. normally, i can figure stuff out but this one has me puzzled. when turning the key to start, engine turns a few times then i lose all electrical power. everything shuts down. not even a dome light. so i take the key out and wait a couple minutes. i hear a hum from behind the stereo and see my gauges go back to regular. that triggers power again and i try to start again. sometimes, it takes a few of these cycles before i can start my truck again. any ideas on this one?

thanks!