How to balance lecture participation and not being considered a show-off? I am a student in a rather small (20-40 students) lecture. This lecture is mandatory for the students of this subject in this semester. In the course of the lecture the professor regularly asks students questions or encourages them to theorize about possible solutions to a problem before revealing the proper solution. Usually only about five of the students raise their hands and give answers. I am one of them and maybe the one who participates the most. I partly studied this subject before so I have a little more knowledge than the others but I am also genuinely interested in the subject while most of the others seem to find it boring and are only there to be able to pass the exam.

I often hesitate raising my hand or don't do it at all because I feel like I answer most of the questions and almost get into a dialog with the professor while all the others sit around me, bored and maybe a little annoyed (I didn't notice any negative reactions). I also usually wait a bit after a question was asked and only raise my hand if nobody else did in order to give the others a chance to participate.

I feel like I am constantly restraining myself from showing to much enthusiasm in fear of appearing as a geek or a show-off. What can I do? 

Possible duplicate: How not to come off as boasting or arrogant, if you are one of the few active students in a class?
(only found this after posting)
A key question is - why restrain your enthusiasm?

Importantly, it does not really matter what the other classmates think of you - you are there for the interest in the subject, not for their approval. As you stated, you have not noticed any negative reaction - it could be a case that a few others in the class are benefiting from your contributions - and more than likely, the instructor appreciates your participation as well.

It sounds like you are polite, holding back and waiting for anyone else to contribute - that is a positive.

If you are still concerned, speak with the instructor, ask them if there are other ways you can help get the class engaged and of course, ask if he/she thinks you are contributing 'too much'.

What to do? Don't change, you have enthusiasm, you politely wait for others to answer before you contribute. (But as suggested before, talk with your instructor about your contributions).

Just to clarify, I am speaking as a practicing teacher