The causes of dizziness and light headedness can be divided on the system, which is involved, and there can be many diseases causing these symptoms;
1) Inner ear or internal ear disease
2) Central nervous system
3) Cardiovascular, or
4) Systemic diseases
Internal ear disease vertigo is termed true vertigo in which one feels rotational movement of self or the surroundings. The false vertigo or nonvertigo has feeling of light-headedness, unsteadiness, motion intolerance, imbalance, etc. You need to consult first a ENT specialist to exclude the diseases of internal ear. They will perform some clinical tests (vestibular diagnostic tests) to establish the cause.
The various causes are;
1) Benign paroxysmal positional vertigo (BPPV),
2) vestibular neuronitis,
3) Meniere disease
4) Immune-mediated inner-ear disease
5) vestibular migraine
6) acoustic tumors,
7) Cerebellar lesions.
To diagnose the cause various investigations like MRI may also be needed. Read the resource;
Please feel free for your follow up questions.