I'm just going to guess... and based upon what PW suggested...

Are there instances wherein you are listening to the stereo at a normal, conversational level, volume?

Are there instances where you might be blasting some metal (ROCK)... and that's when the fuse blows?

Maybe at lower volume there's less amps running. But, when you're blasting those amps go up. I don't know. I failed radio electronics late 70's. Trade institute. Couldn't wrap my head around it.

Have you considered installing, temporarily or otherwise, a different stereo and seeing if the problem repeats? That might be the ticket.

My $00.02

Thanks for the suggestion!

In every instance, the stereo goes out upon starting the car. It never happens during a drive.

Probably last update:

I contacted an electronics repair place, and they said they no longer work on car stereos, nor do they know anyone in the area who does. So I guess I'll have to replace the unit.

That is a big indicator. Most radios have a Switched mode power supply to step up the 12 volts to some higher voltage. This is probably failing when the car battery voltage goes low and then it draws an excessive current to compensate.

Simple but not a good solution is to turn the radio off when starting !!!

Alternatively turn the key on to acc, wait for the radio to start and then start the car. That may give the radio enough time to 'stabilize'

While not ideal, I will try this strategy and see if the problem persists. Thanks for the suggestions!

I'm cautiously optimistic that I've discovered the problem. I was playing mp3s from a thumb drive in this stereo, and since I've removed that drive, I have had no more problems with the fuse blowing.

Maybe pull the Radio and put in on the bench. Hook up 12 volts and check.

Aaaand it happened again. So much for the USB thumb drive theory.

Just bought a boxter. I have a stock radio and the fuse sometimes blows when I start.
My battery also has a draw on it and will go dead within a few day. Not sure if they are related.

I have no clue on the fuse issue but the battery draining problem sometimes may be resolved by turning off the LED in the radio if it constantly blinks. It`s in the manual for the radio how to turn it off.