The cause of sudden dizziness could be low blood pressure, standing up too fast, side effects to some medications, spinning in circles etc.
If you have just experienced sudden dizziness it could be due to lack of sleep, standing up too fast or it could be some medications you're taking.
Most cases of sudden dizziness are nothing bad to worry about and the dizziness usually goes away within a few seconds to a minute.
If the dizziness continues then you should see a doctor about it because the dizziness when it occurs too frequently could be caused by other health conditions.
If the dizziness does continue a lot then you may have Vertigo which is a medical condition and you should get it checked out by a doctor.
However if the dizziness just happens occasionally then it's usually nothing to worry about.
I get dizzy every once in awhile and the dizziness occurs suddenly and nothing is wrong with me although it feels like it.
Also if I don't get enough sleep I get really dizzy the next day and cannot function.
So be sure you're getting plenty of sleep of at least 8 hours but even 6 hours of sleep is better than any less than that.