Bmw cranks but will not start
 BMW sitting for a while then the problem starts.   First check the battery,next check Camshaft sensor.   Replaced Battery it Cranks over but won't start. Also Replaced the Camshaft Sensor   In that case ... most likely a bad fuel pump, fuel filter, or old gas  less likely but possible: problem with he fuel pump power supply, other fuel clog, or ECU/security issue.   Hope this helps.