Since you say this is happening often, it's possible you have some form of sleep apnea where, during sleep, you temporarily stop breathing -sometimes for up to 10 seconds in some people. It can happen many times a night but most people aren't even aware they have it, since they don't usually wake up fully when it happens. Maybe you have it and ARE waking up...at least enough to notice your racing heart (tachycardia) caused by the breathing issue.
You say you are "pre-diabetes". Are you overweight by any chance? A heavy snorer? I only ask this because apnea tends to afflict overweight people more than thinner folks.
zuzu
