Are you getting the "Driver irql not less or equal" error? Or is it "Unmountable Boot volume"? If that is the case, it could be a hardware or software problem. If you can save your data and do a reinstall, that would probably be your best hope at this point. If it is reoccurring after that, then it is a hardware issue.
I would say the majority of times I have seen that error, it was due to a hardware issue, but not always. Sometimes overheating can do it as well, if you haven't cleaned the computer out in awhile, it might be a good time to do so. The typical overheating problems involve fans being clogged, it doesn't hurt to do it, but I doubt it will change much if this error is happening at boot every time.