Kindle requires restart to turn on screen after staying idle 5-10 min.

Hi,

I have kind of a unique problem with my kindle. My kindle does not turn on after staying idle or in lock screen for 5 - 10 min. It does not respond when I push the power button to turn on the screen. However, I can only restart it by pushing the power button 7 seconds. I can continue to read after the restart but then when I leave it idle for 10 min then I cannot open the screen again. I need to restart again to open. I have already tried 2 different battery and also hard reset.

Thanks,