Welcome to HCM!
After reading your question it comes out that you are having some giddiness and lightheaded ness from past 3-6 months but it is not affecting your life.
Had I been at your place I think I would meet a general physician or medicine specialist. To me it appears to be either some blood pressure problem or may be a case of cervical spondylosis
getting your routine tests and BP checked will rule put some usual causes.
You are right in finding for it's cause as even though this is not disturbing you life but this is a symptom and it should not be there.
Anyways, it looks to be only some minor problem, so donot worry a lot, see a doctor. Only after examining you one can pinpoint the reason.
Hope the reply is useful
Feel free to ask more questions
Dr. Manisha Gopal