perhaps a bad alternator?

 

Had any rain lately? Hows your sunroof drain tubes.? Your ecu/bcm is located in the pass footwell when wet causes all sorts of electrical issues. Charging system is simple. Alt good batt good starter good. Check the ecu. Sunroof drains are a well known issue and fail leaving the ecu to.get wet and cause weird non diagnosable issues

 

similar issue on mine, as im working at home now, so don't drive it sufficiently or long enough etc and and it started to happen, a slower start after 3-4 days and then sometimes after 2 days of sitting..so took it on a long drive a few weekends ago and it was good for 4 days and then sat for 2 and slow crank again...finally one day, it got chilly here and went to start and dead...enter AAA and the guy jumped and said it was showing on his app 240cc or something like that , but battery is less than 3 years..everstart from wally world, so plant to take back and see if they will replace, if not going to Costco for theirs , but i recall, car sitting for 1+week when i traveled and no issues, but battery was oem at that time and or this one was newer etc...so maybe those factors and coolish weather , but good luck, as i thought maybe something was drawing current...the only thing i have done over summer was remove console to vinyl wrap, disconnect battery, so i thought maybe something is there and slowly drawing a slight charge..dont know if possible but, will replace battery and see if that fixes it...but may also invest in the tender gadget ...good luck dude

 

Thanks so much for your reply. The 100% dead battery has been fully charged & the car has been running just fine ever since. I appreciate your time & you sharing your knowledge with me!