Absolutely - and that's what matters.
FWIW, my HR has almost always shown weird spikes in the first 5 mins of a run, regardless of which HR monitor I've used. I've speculated that it has something to do with the HR monitor estimating an instantaneous HR/minute by measuring the time between beats in a small sample of a few seconds. When I'm warming up, my heartbeat seems more variable (the word "erratic" seems scary) but then it gets to a nice, steady boom-boom-boom after a few minutes. I've always just ignored spikes in the first few minutes, especially since they sometimes indicate a new HRmax over 200!
Huh. Thanks. Good to know.
Oh, and to resume an earlier chat the altitude on the 235 is calculated without the benefit of a barometric altimeter. I think it runs an algorithm based on feelings in its trick knee. Or maybe I have no idea.
It's kind of like a trick knee. Even though the article is old, DC Rainmaker explains it well - and he links to an HR article too.