Pretty typical of what happens when you take the watch off - the HR sensors turn off after a few seconds if the watch is motionless and it can't detect a pulse.
If you are seeing this while wearing the watch, were you doing anything unusual 2 hours ago.
It happened during my sleep at night (the watch was all the time on my hand) It's midday and There is next gap in the graph... ciq.forums.garmin.com/.../1308847.jpg
It can also happen if you are wearing the watch loosely. Light can get between your skin and the watch's sensor. The watch can get to a weird angle during your sleep and sensor can not detect a pulse. Etc. Try wearing it a little tighter, but not uncomfortably so.
