I used to be too nervous to ask for oral sex. Back when I was younger and with a partner who never did it.
In all honesty, I think the best way to attempt to get over fears and nerves, is to bite the bullet and do it. Unfortunately I don't know of any other way to go from "too scared to do it" to "Doing it" other than "do it" (if that makes sense). With fears or shyness, we often talk ourselves out of things by imagining all the possible things that could go wrong; we could look stupid, someone might laugh, someone might think less of us etc. Notice most of the fears are about what other people might think of us?
I guess you need to imagine your worst fears about the situation. What is the WORST than could happen and then get to a point where you imagine the worst, but it doesn't bother you so much anymore. Someone laughs at you? So what? If they laugh at you, then what...and then what...and then what..Follow that trail until you work out exactly what it is you are really afraid of and challenge that. It is important to us to not come across in ways that make us feel small or silly, but we are human and we all end up doing things like that at some point and the truth is this....if people care and judge you - are they worth it anyway? The people worth it are the ones who love you all the more for your quirks and unique ways about you.
I have a feeling that 100% of men who enjoy blowjobs would be turned on and pleased that you want to do that...for him! Its an ego boost for him and you are giving pleasure. How can offering your lover pleasure be seen as anything other than amazing. If you meet a guy who does not like oral, if anything he will just feel a bit awkward about himself and will feel embarrassed maybe, explaining he does not like it. At no point do you look silly or anything else, other than considerate and wanting to please.
Yeah it is just about challenging your own thoughts and eventually biting the bullet. Keep saying to yourself "I WANT TO DO THIS" and I am not going to keep letting those worrying thoughts get in the way.
Have you tried practising it out loud to yourself? Yep, you will feel so silly and embarrassed at first. Keep doing it until you can say it without any embarrasment. This might help give you confidence too.
Good luck! xx