With my Nissan that's an indication the battery is low in the fob
I agree! It could also be in the ignition switch itself.
The system is trying to tell you something. What that something is, is what we don't know. Look for something simple first like, Oh IDK, have your battery load tested to see if you may have a bad cell.
OR for example, the '06 Mazda3 in my signature, the Engine Immobilizer [SOMETIMES] continues to flash & beep when the engine is shut off and key is "removed"...as if the key is still in the ignition w/door open. All we have to do is, reinsert the key(w/o turning it) and immediately pull out the key again.
It's been doing this for the 8 years we've owned the car! It just doesn't happen often enough to warrant any investigation.