You have a 7 year old computer and you're wondering why stuff might be breaking down? I can suggest one possible fix, and that is
resetting the PMU. Also check to make sure that the Eject key or the trackpad buttons aren't reading as pressed for some reason. If it comes down to needing to bring your computer in, you can give a shot to either place but the parts are going to be few and far in-between for a computer of this age...Apple may have already listed it as
vintage.