I had a problem with a BlackBerry Curve smartphone that would not start up at all. It was restarted over and over again and never brought me to the Home screen.
To solve this problem, you can try pulling the battery from the device. Leave it out for about 20 seconds, then reinsert the battery and try to start the Curve again.
If that doesn’t work, you may have some type of third-party program installed that is causing the problem. Try starting up in Safe Mode by holding down the Escape key (button with the arrow) while it boots up. If it starts up this way, you will need to find the problematic program and uninstall it.