Thanks for posting your query.
There are couple of possibilities in your case like:
1. Positional Vertigo
2. Extreme fatigue
due to physical or mental exertion
It is advisable that you visit your blood pressure and other things needs to be looked for.
In mean time,
-Take proper rest, avoid sudden movements of neck
-Drink plenty of liquids
-Take light diet
I hope this helps.
Wishing you good health.