Have you checked your starter relay........If it an Auto Transmission than worth check if there are any fault codes in Auto Transmission as well........?  Looks like you have intermittent starter relay fault..................you are also having a fault code for your immobiliser key but if the car is starting than that might not be a hard fault.............
 

 yes ash is correct, i did not see this post and i replied to your other one. on this code alone p0615  you most check everything ash suggested if the other code is showing first then an immo issue is most likely the cause or bad bcm, a bad fuse box or ground is also known for code p0615 good luck. do an auto scan of all modules, erase everything and see if you can duplicate the problem and report trouble codes, the first code to pop up is attack first.