My therapist is not a psychiatrist. I can't comment on how normal this is for a psychiatrist, but I believe this is not at all typical for any MD. Whether or not you should ditch him based on this alone is, I think, a matter of how much the scheduling issues affect you and how willing you are to change. What are the benefits of staying?

My therapist sees clients three days a week, mostly in the afternoon and two evenings. He takes a few weeks off every year - a couple of weeks during winter, a couple of weeks during summer and a few days during spring. I wouldn't feel very safe if he took time off frequently on a whim and didn't have appointments available for two weeks when rescheduling.

If you do decide to see someone else, you could discuss scheduling details in the beginning so as to avoid such a situation.