If the CEL comes on, YOU NEED TO PULL CODES
before trying anything else.
The OVP is a prime suspect for this type behavior
See, the low octane gas you put in caused a cold solder joint in the OVP to ,,,
(kidding) seems to me the gas had nothing to do with your problem, unless it was bad gas (unlikely)
I have seen problems like no start, or hard start, or starts and runs then all of a sudden dies all caused by the OVP relay. (One 190e I parted saw the better part of an ax because the PO couldn't start the car, I replaced the OVP relay and started first try)
It wouldn't hurt to ensure that the electrical contacts are clean too. And that there is no corrosion on the ground wires.