Nexus 5

Boot loop: (phone repeatedly shows Google logo, but won't turn on) Typically the reason for a bootloop on the Nexus 5 is the power button sticking. Sometimes it works to clean the power button switch with rubbing alcohol, but often it requires replacing the switch. The button is a 4mm momentary switch which can easily be sourced from eBay by searching for "Nexus 5 power button". The button is tiny and fairly difficult to replace, but is doable with basic soldering tools.

Note: Not to be confused with the Nexus 5X which has a similar problem, but it's because of bad solder joints the main NAND chip