Sounds challenging for a first road race if it had such big climbs. Had you already done some crits?
Presuming you’ve come from a mountain bike background, it’s very easy to get carried away and work too hard before it even gets grippy. Those times when you feel the pace is too easy, or that they’re failing to maintain their momentum, is often because they’re reserving their effort. Alternatively, maybe you sat in the back too much which takes more energy due to having to accelerate back up to speed more after corners. Apologies if you’re well aware of such advice.