My Blackberry Flip 8220 sometimes goes out of power (turned off) by itself. So I have to re-insert the battery to start. ????????

Unless it is a CDMA phone, it should be under the battery.

I hope this helped.

This may be needed:
https://www.wireless.att.com/support_static_files/KB/PATTLNK_1122006_1753-8100c_SIMcard.jpg

you either have a dead battery or an os issue.
Sounds like a corrupted OS once again, try a battery pull if you haven't already.

Next you

Invalid sim means it's locked to a career but your simcard's career, to unlock your BlackBerry go to http://blackberrymep.com and get your unlock code along with unlocking instructions .

try to clean the battery terminal/conector on your cellephone.use cotton buds with small amount of alchohol.If it still does'nt work,try to replace your battery with new one,because batteries are sometime make fool on us.Even though it still have a power within the battery,cp still doesnt open when the battery is already weak its current, or what we call the AMPERE.

take out the battery and it should slide down from the top

If you need further help, I’m available over the phone at https://www.6ya.com/expert/aaron_a0d6f580814d28b2

need to adjust Sim tray try putting something to hold it a sticker or tape some small paper.

I've had the same problem, particularly after upgrading the OS. I've been able to keep it reboot free for 24 hours after resending the service books from the bberry portal (and I'm even using it unlocked from T-Mobile on AT&T).

it is so because ur mobile has some software problem or it is simply a problem a problem is the set
best way u give it a service centre or tell them, to reinstall the software

push the blackberry dot button and scroll to delete

What I would do is turn it off completelly for a few minutes. take out the battery and let it cool down for a few minutes. If you have a battery that if fully charged put it back in and turn on your phone. if your battery is not totally charged, charge it. A phone whose battery is not fully charged may cause your phone to flip out. sometimes it's also water damage to the phone that causes it to turn off on its own.
Water damage happends from body heat, from taking it to the bathroom when you're in the shower, or from putting it directly in water.

Hope this helps.