Definitely check the fault codes, make a note of them, see what they refer to, clear them and see what happens.
If you get a repeat then any codes can help narrow down the source.
From memory, a mate had an auto electric business. He would check earths as a quick first start. More in-depth he would check the voltage/amps on any sensors to narrow down and identify the problem.
I have a Maxiscan OBD tester and it could monitor systems with the engine running. It showed me which O2 sensor of the 4 on the Plus8 was faulty with the engine running. 3 sensors showed voltages stable and the faulty one was erratic.
Not a perfect tester though. The car had MIL occasionally coming on. Everything appeared ok and what cured the "random intermittent misfire" that triggered it was using higher octane petrol as a last attempt after head scratching checking. The engine ran ok and the Gems system used the stats package in it to accumulate misfires and trigger the warning. Stats and electrickery....a marriage made in Hades.
