Flawless, if I understand you correctly, you get to the splash screen with no problem, and then you sometimes go no further.
You might have a hard drive problem. The next time you get in, you need to run a deep scan with your AV. However, if your hard drive is failing, you need to find out how to boot into Safe Mode. Safe Mode makes it easier to get your hard drive started, and that will give you more time to backup before it is too late.