Weird electrical issue today?

Okay so today as I was heading out to lunch from work I noticed the following.

1. The doors unlocked as normal with the hand sensor.
2. However the car would not start. Push button, no response, nothing.
3. Low keyfob bat? okay i put it close to the push button, nothing. Tried a few times, then notice the push start button yellow/orange light up come and one of the lights on the dash comes up, but still doesn't start.
4. Dead 12v bat? I exit the car, and the keyfobs lock/unlock buttons don't work.
5. I get back in the car, and it starts up like normal. I drive home for lunch, it's all good.
6. I head back to work from home, no issues.
7. as I was exiting the car from the work parking lot, I noticed that the lock doors button on the driver door didn't do anything, press it a couple of times and I think i saw a faint check engine light come up and some other red warning light next to it.
8. I start the car, and it starts fine.
9. Doors and all lock fine now.

what's the problem here? 12v battery needs replacement? all original parts except for the engine that was rebuilt due to oil consumption.

 

okay thanks, i'll have to get the bat tested/replaced asap now. hopefully i won't completely fail on me before then!