speakers problem

I bought a new 2004 Corolla and about 3 months after I bought it I was on a highway listening to the radio (had been driving about 2 hours already and wasn't blasting the sound) and suddenly heard a loud, low, pop. It sounded like someone hit my trunk with a bat. The radio display and all sound stopped and then went back on, and it would continue to pop like this every few seconds. I turned the radio off and right back on and it did this again after a few seconds. So I turned it off for the remainder of the trip and was able to use the radio normally for the next year until it happened again twice in one week.

It was ok for about another 8 months and then popped like that about 5 times one week during <5 mile trips. Its been OK now for the last 2 months. My question is, what is this and why is it occuring? Should I go see about having this repaired? Is it indicative of a serious electrical problem? I just don't want to go there and have them not find anything wrong only to have this happen again =(

Thanks in advance for the help!

Sounds like a problem with the head unit itself. The head unit in these cars is the amplifier for the speakers so if all the speakers are going out at the same time I'd go to the source, which is the head unit. You said the car is a 2004, isn't it still under warranty??