Is it acceptable to begin a paragraph with the word "also", in the instance of continuing an argument with a new paragraph and new idea?
It's probably all right. I might suggest other words in context, to show a complete change of topic. Maybe "furthermore" would work better. "On the other hand" would certainly work, so "also" might. It's hard to tell without seeing a concrete example.
Also, I think it's rather informal and weak. Wouldn't you agree, seeing it like this?