[Tony Maldonado]

I have a Priv. It is attempting to reboot over and over again. It can't get past the first screen, then it goes black and starts over again. I've tried pressing the power button for varying amounts of time.

[conite]

If you have a case, it may be pressing against the power button.

[erose75]

Have you tried plugging it in and letting it sit for a few hours? Some others have had luck with this.

[FF22]

From BB blog: How to reset PRIV by BlackBerry | Inside BlackBerry Help Blog

Three restart/reboot methods

The first method, which should be used 99.9% of the time when you want to reboot your device, is using the Reboot option that appears after pressing the Power key.

Press and hold the Power key for 3 seconds
Select Reboot from the menu that is presented

The second reset method should be used if pressing the Power key does not produce the menu with Power Off and Restart. For example, if an app or game you are using won’t close, use this option to restart your device.

Press and hold the Power key for 12 seconds

Third method: Should your device fail to respond, the final reset method is to press and hold the Power key for 32 seconds which is equivalent to removing the battery. This should result in your device booting up successfully.

If it fails to start, however, verify you are not pressing any other keys such as Volume Up, Mute, or Volume Down while performing any of the reset methods listed above. If you use a case for your device you may want to remove it as it might be pressing a button inadvertently.

And just for an extra measure, if needed:

Safe Mode:

The next step is placing your device into safe mode.

When used, Safe Mode will disable any third party apps or games you have installed. As a result of this, should your device not exhibit the issue while in Safe Mode it’s safe to assume the issue is specific to an app or game you have installed. Safe Mode may also remove apps and/or widgets from your various home screens when you go back to Normal.

Press and hold the power key
Tap and hold Power off (that is Press/Hold the Power Off prompt line) when it appears
When prompted, tap OK to reboot to Safe Mode

To get out of Safe Mode, press and hold the power key followed by tapping Reboot.

After testing, should your device not exhibit any issues, the next step is to remove recently installed applications one by one until the issue is resolved.

[Tony Maldonado]

I took it out of the case just to make sure. No help.

[Tony Maldonado]

Yes. Been on it's charger for 18 hours. No change.

[Wezard]

How does the power button look, and feel? There have been a couple of reports of volume buttons getting stuck, and having to be 'pried out'.
Next, make sure your charger and cable are good, cables go bad a lot. Plug something else in and verify that it's still working, just because it worked last night doesn't mean it will work today.
Then charge for at least an hour, and while still connected to charger press and hold power button for at least 32 seconds.

If that doesn't work, you may have to run an autoload. I think it can be done in the condition you describe.
If not, somebody will jump in and correct me.