What Causes Intermittent Dizzy Spells?

for years I sometimes get weird dizzy spells, I could be laying down, walking, eating even sleeping.. things seem disoriented, things seem far away, and not real, at times I can even feel for stomach sick.. only last a few seconds, however it occur many times a day, for a couple of days.. it may not reoccur again for several weeks or months. it has been happening for years.