I started much heavier than most of you (440 when I started, 400 when I got my bike) and I felt self conscious right up to the point that I got on my bike. I thought about it a lot earlier, what am I going to look like, are kids going to laugh, is anybody going to make snide remarks, etc. None of that happened, and I live in a european country where there are a lot fewer fat people, flat out. I'm the biggest person I know, and have been for many years.
Anyway, my first ride in 18 years was 13km from the bike store home on one of the first really nice saturdays of the year - that meant the sidewalks and bike paths were full of people. Nobody stared, nobody said anything, they were busy doing their own thing. Heck, even if they did say something, by the time they got it out I had already ridden by.
Now I'm up to averaging 20km/h on my MTB, gonna get a road bike for next year when I'm closer to 300lbs than I am now (365).