Improperly starting 04

Our Prius has a funny quirk, one that we can live with because it only does it occasionally, but is still quite annoying when it happens.
Sometimes, when the car is started, it does not turn on the electronics correctly. Most of the stuff still works, like the radio, GPS, etc. But when it does this, the only light that shows on the console is the check engine light (which is on for some coolant sensor that we don't need to fix right now) is the only thing lit. Nothing else, including the gas gauge and odo and MPH gauge, lights up. On the Consumption screen, it also does not register miles driven, avg MPG, and does not track anything. The energy screen works fine, although it does not show current MPG, as if it doesn't really know the car's all the way on.
Only totally random stuff makes it stop, such as driving a short distance, turning the lights on, entering maintenance mode, or restarting it. (This problem usually prevents the car from shutting down, also, which can be quite annoying.) Fortunately this doesn't seem to affect the car negatively in any was other than not knowing how fast you're going.
Any ideas? Sure a weird problem. Dealer didn't pick anything out reading codes, and it doesn't do it all the time (although short starts, such as turning on to roll down windows, usually seem to cause it.)

 

I've thought about it but I've been in maintenance mode so frequently and that tells me the battery voltage. Is it accurate on that screen? I will go ahead and check it, though, as soon as I have access to a multimeter.

Thanks, that's very good to know. I'll take it in and have them check on that. It's not a serious problem, at least it doesn't seem to be, but highly exasperating. Also, sometimes the MFD won't shut down after the 3+ seconds.

Thanks!