If it is just at times, particularly when you are active or when you are anxious, it's probably just an anxiety and/or activity thing.

For context, my husband has a heart condition where his RESTING heart rate will be 160bpm for hours on end and they have to make serious interventions to get it down. THAT'S a serious issue with heart rate and will require a cardiac ablation to correct. I also have a cardiac palpitation issue that flares up from time to time. It is rather benign - mostly annoying. I do have medication I can take for it when it becomes an issue, but even it isn't a serious cardiac concern other than an annoyance.

100 or so on occasions for short periods of time, particularly if you are having anxiety, is probably NOT a serious cardiac issues so much as an issue of anxiety that you need to address with your therapist or psychiatrist.

You may also consider less sugar/salt in your diet as a healthier diet may help with the dizziness and even the anxiety. More fresh fruits and vegetables. Less mountain dew and fast food.