Why would I sometimes get dizzy, shakey and a feel a rapid heart beat all of a sudden?

Many reasons. You may have an arrhythmia, or you may simply be dehydrated. If the rapid heart rate comes first, then the dizziness, arrhythmia is more likely. Please discuss this with your primary doctor, relief from your symptoms is very likely once a diagnosis is made.
Rapid heart beat. Palpitations with symptoms of dizziness should be evaluated by cardiologist. It could be atrial fibrillation, supraventricular tachycardia etc.

Related Questions

I am 19 years old. I have dizzy spells when I get up from bed and taking hot showers, abdominal pains ocassionally, rapid heart beat. What can this be?

Lightheaded. Might be as simple as dehydration or not enough water intake. See your primary doctor for further evaluation to be sure.
Spells. Your symptoms sound like drops in blood pressure. Sometimes this is termed orthostatic hypotension or neurocardiogenic syncope if it leads to actual fainting. Have your doctor check your pressure lying down, sitting up, and standing.

My 15 year old daughter developed rapid heart beat and extreme dizziness two weeks ago the dr says its anxiety can it last that long its everyday?

Palpitations. Hope treatable conditions like hyperthyroidism, svt, anemia etc are ruled out. Hope she is not using drugs, or too much caffeine and is well hydrated. Make sure treatable conditions are ruled out.