Matthew.
The only thing I can think of that causes electronic problems without yielding error codes is a failing battery. Typically such a battery will cause problems like aircon failure, cruise control failure, loss of radio presets, false warning lights etc. I have never heard of it interfering with starting. Nevertheless I suggest you get the battery tested with a deep discharge tester, and if it is over four years old I would renew it anyway. Ensure the new battery is coded to the car if you change it.