Why does my phone keep giving me the message "Android is updating"?

I found the phone from a long time ago and it was stuck on the t-mobile screen. I looked up solutions for that and ended up doing a hard reset. It didn't work the first time, so I did it a couple more times, and I've probably done it a dozen times by now. Now, it stays on the t-mobile screen for a few minutes, then says "android is updating". It plays that message in an endless loop until I have to take the battery out. I don't have a sim card or anything in it, just the battery, but I'm not sure if that's the problem or not? Any help is appreciated!!