Update: not solved
I got a new key from the dealer, everything was good for about a week and then once again....came out from dinner out and wouldn't start. I listened carefully and it seems like the first time i turn the key there is a distinct click which sounds like it's coming from the starter like it doesn't have enough power to engage. then on subsequent tries there is no noise at all. this last time it started after a few tries. then the next day i went to start it and it started, but it went into limp mode and threw 10 different codes at once. I had my obdII code reader with me so i logged the codes and erased them. It has started and run fine for the last couple of days. The codes seemed pretty random, 1 for the thermostat, 4 for the vanos solenoids, and the others for fuel pressure and cam and crank sensors.
I have replaced all of the cam sensors, cleaned and replaced O rings on the vanos solenoids already and it has a new thermostat and sensor. All of which have been working for 5-6 months with no issues.
Could a bad crankshaft position sensor be causing all of my starting issues? it seems unlikely to me.
I'm hoping the next time it doesn't start I will be in a position to test the starter relay and the voltage to the starter solenoid. Every time it's done this I've been out somewhere with no access to tools or equipment. One thing I have noticed is that it seems to occur when I have driven and stopped at several places within a short time period, like going to several different stores in an hour.
thanks