For what reasons has my heart stopped and started like 4 times today?

Palpitations: It sounds like you are feeling extra beats, which often feel like a pause. See your doc. You may need to wear a heart monitor to see exactly what is happening.

Hard to say: Why not look into it? The usual evaluation would consist of an ekg, echocardiogram, stress test, event monitor (24 hour to 30 days as needed), and blood work to check your electrolytes and thyroid function. While they're at it, your glucose and cholesterol could be checked as well!