It's normal to have a bad day out of the blue. I was concussed in April, LOC 45-90 seconds. Was in a fog for 24 hours after being released, then the fog lifted somewhat. Started getting random dizzy spells getting up from bed, rolling over in bed, etc. Turned out that the concussion exacerbated my nearly lifelong vertigo. I underwent neuro rehab, the tech recognized my symptoms were vertigo, and corrected that (about two months ago). But April to July were not fun. Best of luck to you.