Is it normal for a man to have an erection when he wakes up?

A good sign: Having nocturnal/sleep-time erection suggests normal physiologic response and that yours is still functioning normally. If you have good nocturnal/night-time erection but can't during awake time to perform, then some psychological factor is inhibiting you. If you do have trouble, consult doc. Good luck.

Very much so: This is more formally known as nocturnal penile tumescence and is something that very common. Don't be alarmed by something like this.