I got my period 4 days late and when I finally did get it it was only spotting for 4 days on and off what could that mean?

Is pregnancy a possibility? May just be an off cycle, which can happen now and then. Are you on any sort of hormonal birth control? That can sometimes cause irregular bleeding. If you are older, might be due to hormone changes.

You could try a pregnancy test, if that could be a reason, or wait until next month and see what happens when you would expect your period.