Backup all your saves and anything else you don't want to lose on a USB and put your PS3 into recovery mode (
). Then choose the option to reset everything, the video will tell you which option that is, I can't remember which one it is. Most people say that doing this will fix most problems but there's no guarantee that it will, definitely worth a shot though.If that doesn't work then you'll have to call up Sony and ask about getting it fixed or replaced. Is the warranty still valid on it? Otherwise your looking at about 130 quid to fix/replace it.
Best of luck, it's never fun when your console starts acting up.