I am new on this forum and have been looking at some of the other answers for any advice but I seem to be stuck in a grey area.
I met a guy a couple of weeks ago in a bar, I could tell he noticed me and he came over to me later that night to try and have a chat. My friends told me he does this with every girl so I didn't really make much of a big deal of it.
A couple of weeks later we got talking again (up until the bar actually closing and us being the last two in there) and we walked home together. I felt we got on well but he didn't ask for my number at the end of the night.
The next week again he was staring at me and I am pretty sure he is attracted to me so I decided to leave my number for him saying I needed some help with a project I have.
He calls me and we arrange to meet up for some lunch - we saty talking for around four hours but I still can't tell how he feels. He had the option to not call if he didn't want to and he didn't have to stay that long but on the other hand I felt he seemed unrelaxed and nervous.
There is an age difference between us (he is over 10 years older than me - I'm 23) and he has not had a girlfriend apparently for over 10 years but I just don't understand why a guy who does seem attracted to me isn't "seizing" the opportunity. Do I need to make myself clearer? I myself am quite shy so this is a difficult situation for me.

What is it you want him to do?
Call you for a second date?

It would be nice to see him again in a more relaxed situation as I felt there was some arkwardness today. Is it possible the guy could be shy beneath the act he puts on?

Simple truth is if he wants you he will come and get you. Other wise he's just not that into you!

Yes. It's possible he's actually rather shy and if you are shy that makes it harder. Two shy people have a hard time keeping a conversation going. You may have to make an effort to be less shy.

I think 4 hours for a first date is much too long. Plan some short fun activities that have a definite end. Do something where you don't both have to be ON all the time, where you are more outward directed, like an amusement park or a museum, where there is lots to look at and trigger conversation. And you aren't face to face every second.

Also, think about his tendency to go up to lots of women and what that might say about him. You haven't told us enough for me to tell if that's a bad sign.

I am going to speak from personal experience, and I think you hit it on the head and did not realize it. He is 10 years older then you, and as someone who has dated girls 12 years younger then me I did exactly what he is doing. Younger girls tend to be flaky and inconsistent with their words vs. behavior so I believe he is very interested but at the same time taking time to make sure this is something he wants to follow through with.