Random heart rate spikes during sleep
According to my tom tom touch, I frequently get heart rate spikes well into the 140s during my sleep. This doesn't happen during the day, just at night. It seems incredibly unlikely that this is my actual heart rate, given that I'm asleep. I've found previous questions where people have had this issue while running, and that the heart rate monitor has detected their cadence, however I think this is also unlikely to be the issue since I'm not running when it occurs.
What could be causing this problem? Is there something I can do to prevent it (wearing the band tighter/looser or elsewhere on my wrist)?