Radio or Amp Not Working Properly

I'm new to this forum, so apologize if this has been answered before, but I tried searching and didn't come up with anything that seemed like my issue. I recently had my factory radio on my 2008 4 Runner (JBL) with a pioneer AVH 36000. I didn't want to overhaul too much so I just had them hook directly up the existing factory amp. Everything works well 95% of the time but in the last two weeks that I have had the radio, the sound has just randomly cut out. The first time it happened was the first day that I got it, and I overlooked it. It happened again today, and despite trying every input I have and turning the unit off then back on again, it did not produce any sound. However, it appeared to be acting like it was in playback mode for all input sources. I even thought that maybe it was going into mute so I adjusted the volume and hit mute on and off and nothing happened. Finally I simply shut the engine completely off and turned it back on again and that did the trick.

I'm leaning towards this being a problem with my amp considering the randomness and such, but I'm not sure exactly what would cause this. I'm guessing that most amps have some sort of auto shutoff switch if they overheat. However, I was listening at relatively low volume today compared to what I normally do.

I'm going to take it back to the place that installed it and talk to them about it, but I just wanted to have an idea of what it might be before they take a look and tell me my amp is hosed or something like that.