Could be an intermittent elec. problem, like a bad solder joint.
You have a better chance of fixing it if you can reliably reproduce the fault.
This problem can't have too many candidates as a point of origin since you have no other symptoms.
Your local library might have books that mechanics study to pass their ASE exams, and these are full of good ideas as to cause and effect; the problem is the books are not arranged to be used in this manner.
Also, dealers have a data recording device which they deny having, that they hook up and then when the fault occurs as you are driving around you press a button and the device stores what the car's computer was thinking just before the fault.
It's a specialized version of one of these.