I experienced side effects after taking finasteride. But honestly, this sounds like nocebo.
Morning wood isn’t an indicator of anything. If you don’t sleep well, no morning wood. The side effects usually present after a week or so. In my experience, after a month. Instant sides are almost always nocebo.
That said, I don’t personally see any benefit in taking oral fin. If you can afford high quality topical fin, it’s much safer.