My fastboot used to work great, but recently even with fastboot turned on it takes forever to start up. It just freezes on the Thunderbolt image with the bolt in the background. The phone also runs extremely slow. I've killed all non important apps in the background as well as cleared data and done a reset, but freezes up all the time. I thought this was a flagship phone.
Ty2295, I understand how frustrating it can be to wait for a phone to boot and freeze at random times. About how long is the phone taking to boot up? Did this just start after a software update or after making any changes to the device? When you said you did a reset, did you do a hard/factory reset? Try also booting the phone into safe mode to see if this occurs. Other than booting up, when the phone is freezing, is this happening when performing any certain tasks (messaging, calls, internet, etc)?