Every time I switch my phone on, I get the message "Android is upgrading". But it only shows for a few seconds, then the system continues to start up as normal. Obviously Android is not being upgraded. What is going on?
If you are able to get into the recovery you should always try to clean cache before doing a factory reset. Cleaning the cache can at times be the only solution you need to the issue. A Factory Reset should always be a last resort.