Get Holter and sleep study

Heart rate variations exist through out day and also vary according to posture. Blood pressure also fluctuates. Fever , anxiety , hyperthyroidism can cause an increased heart rates. Abnormalities in heart rates are called arrhythmias. They are a variety but mostly in these conditions heart rates are higher than what you mentioned and can be irregular. These are generally monitored with a test called Holter. But in your case the variations seems to be normal. But a thorough consultation with an expert should help eventually.