I think we need to clear up the "no power under the hood when it happens" first. but if it starts in neutral then sounds like neutral safety switch, maybe try to do a forum search, someone else just went through that. You need to do a little more diagnostics or it's going to cost you a fortune in parts!

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)