1. Uninstall all the apps you have installed in the previous few days (ever since this problem started)
2. If you turn off Wifi/Data does the reboot stop ?
3. Where are the pictures? On an SD card or on the device itself? If SD card, it could be corrupt or very slow. Remove card and try if it solves.
4. if that doesn't work, a factory reset should help. Backup & reset. See if that helps.
5. Remember to install apps only from Google play store.