I don't remember if I started at 25 or 50mg but was having a lot of the same issues. Something that helped me with the stomach side effects was to eat before I took the morning dose. Taking it on an empty stomach seemed to make things several times worse. Also, in the afternoon the stomach side effects would peak again so I would make sure to eat before it happened.

I didn't experience agitation per se, it felt more like a jitteriness, over awareness, or being on edge. It reminded me of accidentally drinking too much caffeine. It eventually went away. I think it it because antidepressants can be stimulating at times.