Get a bike. Ride it.
If you need training wheels, use them. If you need to lean against a building a pedal along a 3 mph, do it. If you need to paddle along with your feet on the ground and then coast for a while, repeatedly, until you feel comfortable balancing, do it.
Just Do It.
or do not, I guess.
I don't live life according to what others think of me .... or what I imagine they think of me, because All the scenarios you are playing out in your head about being in embarrassing situations are All in your head .... just your imagination.
Go to a church parking lot on a Tuesday night. Go to an elementary school after it has closed, if their ball field is smooth enough. or whatever.
The sooner you start, the sooner you will be enjoying riding a bike.