Why would you need to copy data from INSERTED into a #temp table?
Why would you NOT know the names of the columns, when they are the same as the column names on your database table?
What you are doing does not make sense, and is almost certainly a bad design.
Why don't you tell us what you are trying to do, and maybe we can suggest a better way. But if you are trying to create "universal" trigger code that you can apply to any table - bad idea.
If it's not practically useful, then it's practically useless.