In the passed few days I have encountered an issue I've never had with my e60. So far twice within two days (not directly after one another, but sparatically) when I put my car into reverse, the engine rumbles a bit then the needle in the rpm gauge hits 0 rpm and simultaneously, the engine dies and the steering wheel locks. No error messages or dashboard warning lights to indicate why this happened. No check engine light on ever in my time owning this car either. Any insight or ideas what it is would be much appreciated. Thank you.