I mowed grass with push mower and heart rate got upto 180 i felt dizzy and short of breath i quick and back to normal but tired is this normal?

Time for an MD visit: This is not normal, I would recommend that you see a doctor for an evaluation. It could be an irregularity within your heart that heeds to be checked out.

Heart Rate Onset?: Onset, is the speed at which a heart rate rises to the very fast rate. When exerting yourself, your heart rate will take nearly a minute to get up to its peak rate. It may reach that faster rate quicker, if you're dehydrated, but if your heart rate "jumps" to 180, within a couple seconds, that's not normal & you may have an arrhythmia. See a heart rhythm specialist ASAP. Call 911 if passing out.