Sleeping Problems
The heart rate [12] usually drops during the NREM stages of normal sleep. It picks back up in the morning as you start to wake up.
Lack of sleep can induce heart palpitations. In a study [13] with women aged 40 to 64, those who had trouble sleeping were more likely to complain of heart symptoms such as irregular heartbeat. If your sleep is poor or punctuated by moments of consciousness, you may also experience sharp increases in your heart rate.
Experiencing nightmares during sleep can also cause you to wake up with a palpitating heart. In a study [14] involving older adults, people who had frequent nightmares were more likely to suffer from irregular heartbeat and palpitations.