I didn't manage to post this as a reply, but here are a few examples of using "hålla" without "i". But this is not important to remember for now. Warning: non-native speaker.
Jag håller en kurs = I am teaching a course.
Jag håller med = I agree.
Jag håller på att = indicating that you are doing something. (Jag håller på att laga mat = I am cooking)
Vad håller du på med? = What are you doing?
In another discussion thread about håller, it was said that håller i is like "hold on to", but when I translated this as "I am holding on to the plate" it was marked incorrect. I am overstating the issue in English or is the "i" just used when something is held in the hands? Tack.
It can mean "to hold onto", but I think those words carry more urgency, like you're holding onto a ship so you won't fall into the water or you're holding onto a golden plate so thieves won't steal it. This sentence doesn't really give me that feeling out of context, it just makes me think of holding a plate, without there being anything more to it.