How do I get out of a boot loop with an iPhone with a broken power button?
ok, now i have this same problem but have found a solution that is not for the people who are shallow to technology...

Step 1: Connect your iPhone 30-Pin cable to your computer. (lightning adapter for iPhone 5 and up)

Step 2: Wait for the device to begin another loop.

Step 3: When another loop begins, hold the home button, volume up button, and plug the charger in.

Step 4: Fix whatever is making the device loop.