Hi, first of all I've got to throw in a waiver:
It can be a REAL bad idea to start a relationship with someone you work with particularly if things don't always go well in the relationship (as they don't always in any relationship) or if things fall apart (and first relationship, they don't always work out do they, step on the road?).
BUT from my less "sensible" side if there's a guy who breaks through all those "barriers", REAL feelings, REAL spark, REAL connection then you're going to know if he's worth it.
I don't know if you're over thinking or over worrying about the whole relationship bit though. Nothing necessarily wrong with building the friendship a little more and seeing where it goes from there. And you wouldn't mind spending more time with him anyway would you?
While, in my opinion, there's nothing wrong with making the first move just saying something like "look I really wanted to go to...but noone to go with and I don't fancy going on my own, you wouldn't like to go would you, OK if you can't but...." doesn't even have to be seen as making the first move.
And lees of the "doomed to failure"! IF it doesn't go anywhere then that's more going to mean that he's just not the person you thought he was, and we all misread people from time to time, we're not going to find out if we don't try though are we.
It is probably going to help if you have more of a think about (if you haven't already) why the low self esteem. Maybe challenge the causes of it, maybe focus more in on what's good about you and achievements (plenty, I'm sure!) and work on the self-confidence. And think a bit more about whether someone deserves to be with YOU rather than whether you deserve to be with THEM.
But hey, rejection can be out there for all of us, perhaps see it as a good things and a release towards you being able to take that next step towards finding the REAL deal, the REAL important things in your life, the REAL important person/s in your life.
No need for embarrassment, just take real strength in the fact you tried and be real proud of yourself in the fact you tried.
The less sensible side of myself REALLY hopes it works out for you!! but do bear in mind the waiver I said at the beginning if you think it might be a better idea to bring more people into your life from outside of work and look towards a relationship in that direction instead?
Best wishes
Alison