Heart rate can increase in multiple conditions..some of them are physiological or let's say the body's normal response to certain condition/situation e.g., stress, exercise, even excessive caffeine intake.. another common condition is hyperthyroidism (high
thyroid hormone levels)
Also machine can malfunction and can show false high heart rate as well .
You can manually check it by checking your pulse for 1 min.. (either near wrist below thunb or neck where you can feel good pulsations)
Next Steps
As there are so many variables which affect the heart rate, it is best to consult a good general physician if your heart rate is persistently above 100 even when u r resting
Health Tips
Relax.. reducing stress will help.. avoid excessive caffeine and start meditation and deep breathing exercises.