Does it happen when you get in the car and start it up? I’ve had this in the past and I’m pretty sure it was the alarm battery being low. Does your car sit for a long period of time?
I think it's usually perhaps a few minutes after driving, but I can't be sure of that. My car doesn't do long distances but it gets used most days. I haven't had any other symptom that there's a battery problem though. I'll have to keep an ear out and see if I can spot any pattern to it!