If you hear the fuel pump engage (faint whining noise) when you turn the key to the ON position, it’s not your main relay. If you hear clicking when trying to start the car it’s not the starter, if you’re not hearing clicking then it may be the starter or solenoid. If it’s cranking but not turning over it could be the battery, which are sometimes funky like Stunna said. Unlikely it’s the alternator, if the battery wasn’t getting charged you would have noticed the car behaving differently over the past couple days.
Ignition I’m not sure about. You could try resetting the ECU then make sure the front wheels are straight and try starting it again.