12.2V is around 40% SoC for an AGM, starting to get low. Fully discharged AGMs will read under 11.8V and they'll start getting damaged much further beyond that. I'd recommend charging it up so it reads above 12.6V while the vehicle and all loads are off. Once you know your battery is at a high SoC, monitor to see if it continues.
You can charge the battery if you have a 3rd party battery tender, or keep the vehicle running for at least 2.5 hours up to 5 hours in Drive mode or Service mode (hold START down for >5 seconds). AGMs can't charge more than 0.4C and typically charge at 0.2C, which is problematic if owners DCFC, drive infrequently or make short trips, and leave the car parked at a low SoC for the high voltage lithium pack (<20% is typically considered low).
If you level 1 charge for a night, then that will also take care of the AGM, as the APM will provide 13.2-14.8V to the battery and contactors during charging, but I don't know your park & charging situation.
Can you provide more details about the parking spot? Is it in a driveway outdoors, on curbside parking, indoors in a garage/underground parking, etc? Are people able to walk by the car, does it ever park plugged in (likely not from the AGM info you gave, unless it has gone bad).
The only time my alarm goes off is when other drivers mess with my Spark during charging. They unplug me from public chargers because they're mad that all the spots are used up, or I'm the only one charging and they want to mess with EVs, which has happened to me at least 4 times in the past 2 months at the mall... Speaking of which, I finally caught one driver, who drives a Mitsubishi i-MiEV, thanks to a Tesla Model X's footage. Turns out the i-MiEV driver has their own level 2 EVSE at home! However, according to him, their son comes to charge in a 1st gen Smart ForTwo Electric, and so when it's busy at home or he prefers not to pay for electricity, he must come to the public chargers to charge his own car. Which is fine, until he starts unplugging other EVs...