This is what I did to try and save my Droid Razr HD that one day rebooted by itself and would not exit the Motorola logo.

First try to boot into Recovery.

To do this, first turn it off. If you can't get it to turn off, press and hold both the power and volume down and wait until the screen goes black (this can take more than 10 seconds).

Once the screen goes black, IMMEDIATELY, press ALL THREE BUTTONS (Power and Volume UP & DOWN) at ONCE and HOLD them until a white text on black background screen appears, then release all.

This screen is called the Boot mode selection menu.

You should see a list of menu selections, and one should be Recovery. The menu is only displayed a few seconds so you may have to repeat the procedure a few times until you figure out exactly how to do this. It is best to read this section a few times until you know exactly what to do.

Press the Volume DOWN button until Recovery is highlighted. If you pass it DO NOT PRESS Volume UP…instead keep pressing Volume DOWN and it will start back at the top again.

Once you have Recovery highlighted, NOW press Volume UP to select.

The screen will go BLACK, then you'll see the Motorola Red Circle with the M, and then the screen will go BLACK again for a bit, then you'll see a Green Droid on its back with the belly open and a Red Triangle with an Exclamation point in the open belly. This is known as the “Triage” screen.

Now press Volume up and Power buttons at once and release.

Now you'll be in the Android system recovery utility screen with Blue text on a Black background.

The Volume buttons here both work for up and down. First, I'd like you to try simply wiping the cache partition by highlighting that line and pressing the Power button. Once done, highlight the reboot system now selection and press Power.