G37 Electrical poltergeist ??

[Spyderspyders]

Drove to store, shopped, came back and car wouldn’t start. It was like a near dead battery where it would make a tktktktktktk sound. There was the red car with a key in it flashing in the console. Door locks worked. Put jumper cables on it and it wouldn’t start. Put a boost jump stater on it and it started.

Had the battery tested and was told it’s fine. Put a new battery in keyfob.

Next day it started fine.
Took it to have alternator / battery tested and was told they couldn’t find a problem.

Drove 37 miles home. Then 45 miles to a meeting and back

Next day car wouldn’t start.
Dome lights were flashing. Red car with a key in it flashing on dash. Made the tktktktktk sound. Battery light - seatbelt light - airbag light were flashing. A yellow key light came on, then went off. Dome lights turned off.

Low battery? BCM? Key fob? I’m clueless.

Thanks for reading!
Please Help!!

[Spyderspyders]

Decided to try buying a new battery, even though I was told 2x it was ok. So far so good.