S3 Power button not working

[Android Question]

Since yesterday my phone has randomly been restarting by its self and when I pushed the power button the shut down menu would appear or it wouldn't work at all.. Today the power button completely stopped working and my after like an hour my phone just turned off my its self and now I can't turn it back.. I don't think that my phone broke cause it's charging just fine, but I can't turn it back.. Heeellpp!! Btw I have a Samsung Galaxy S3 Mini