X3 not cranking. Battery good. No clicking at all. How do i troubleshoot?

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2006 x3 not cranking at all. Battery fully charged. Sudden problem no symptoms or warnings. Tried starting in nuetral. Made sure its in park. Tried jumping and let charge one hour. No click or nois at starter when turning key. Tried shaking car. Tried locking and unlocking several times. I only have one key, key needs battery for auto lock. No abnormal noises or starter noises lately, only brakes are starting ti go slight grinding. How can i troubleshoot to get it started?

How long has your 2006 BMW X3 had this problem?

Just happened suddenly