Are you warming up properly?
There are many ways to effectively warm-up for a workout or event. It pays to spend a little time experimenting and working out your go-to warm-up protocol.
Start with the idea that the warm-up has a purpose--to get you ready for the efforts ahead. As such, different activities/events will have different warm-ups.
For low intensity workouts, warm-up format is less critical and usually can be shorter. Often, you can continue to warm up through the early part of the workout without any negative consequences.
For races & high intensity workouts, it is usually necessary for the warm-up to get you fully ready for hard efforts. As such, the warm-up may need to be longer and/or more intense.
Finally, note that it is possible to warm up "too much". The warm-up itself produces some fatigue, so make sure it is only as long and hard as necessary and that you include at least 10 minutes of very light effort before you begin a meaningful effort (in other words, hard efforts made during your warm-up can negatively impact race performance or subsequent effort output).
Fuel your warm-up! You are burning calories and carbs as soon as you start pedaling. Don't let your warm-up deplete your tank by not taking in calories during this time or at least accounting for them in your overall fueling strategy.
** Note that workout warm-ups are useful for developing an effective pre-event warmup. Use workouts with hard efforts as an opportunity to experiment with different approaches to getting fully warmed up and prepared to go as hard as necessary.