Sudden, "strange" reset of Galaxy Nexus i9250 during playing game

I was in the middle of playing a game, when my Galaxy Nexus, when phone suddently reset itself.

It was a very "strange" reset, because:

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  shutdown phase of entire restart process took less than 1 second,

  
  


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  there was no normal battery vibration at any point of reset process,

  
  


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  entire shutdown-startup process took approximately 50% of normal time it takes to restart,

  
  


• 
  

  I was not asked to enter my SIM card's PIN after end of startup phase -- phone shown just a regular unlock screen, and when I unloced it, I saw, that SIM card is already connected to the network, showing signal strength, while it usually takes it 3-5 seconds during normal restart,

  
  


• 
  

  there was no standar "Google" logo in the beginning of startup phase -- immediately after shutdown (if it was shutdown at all), after less than one second (see point one) phone started to display animated Galaxy Nexus logo.

  
  

This thing happen to me only once so far, so I'm not asking about bug or how to handle this situation. I'm just curious, what was that, I what I noticed? Can someone shed some light on this?

BTW: This is second strange thing, that happens to my phone during past week. Is my Nexus getting too old? :> And should I start to think of replacing it? Are smartphone meant to run over three years? :>