The tv keeps turning off by istself

You may want to try upgrading the firmware. My Philips plasma set did the same thing and a firmware upgrade fixed it. The procedure is simple enough, just copy some files onto a USB drive and let the TV update itself. The release notes give detailed instructions. I couldn't find your exact model number on the Philips site, you'll want to get the correct firmware for your set.
http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?ctn=32PF5321D/37&scy=us&slg=en&mid=Link_Software