Search Results: shy when alone

So we do "Body Attack" together so we see eachother like 1-2 times a week and we have not spoke until one day.
My friend wanted to workout with me but "Body Attack" was too early for her and she wanted to go to the class that was two hours later so I just waited for her.
Turns out he did two hours in a row (Body Attack + whatever that was later) so he saw me and approched. We joked about how one workout was not enough for us and he told me he liked the (guy) trainer from the 2nd class he did and I told him we will see eachother next time.
After that it was mostly just us waving at eachother but we did spoke the last time about the gym again (like really spoke, not just hello)
The problem is: I got really friendly with the women and we sort of sit together mostly before class so I assume he is shy about it but it won't be too hard for me to be alone (check out my reflection and such)
I am not that bad looking (I mean still could lose some weight but I am making a progress and he sees me every week so if everyone noticed that I am sure he has noticed as well) and he is like one of the few guys I find attractive.
He is super bulky and buff (I really dont like lean or thin guys) and he has a nice face as well.
So how do I go from a girl he randomly talks to at the gym to someone he would be intrested in seeing outside of the gym?