I have a 2006 also. I have found if the starter does not turn the engine over fast enough... it will not start. Could be a starter problem or a bad connection in the wiring !
Sorry... it is a code reader. A device you plug into the diagnostic port located under the dash by the steering column . It will read your computer and give you the failure codes that are stored there. You can get one on E-Bay fairly cheaply. The more expensive ones, the more info they will reveal.
This problem seems serious enough to store a code in the computer which should lead you in the right direction. You can purchase a decent code analyzer for around 50.00. I wouldn't suggest to invest in an expensive reader for the average consumer. One of these should do the job.