I know you will probably want to immediately skip this suggestion I'm about to make. But really, there is no harm in trying it, and it just might work.

Go get your bike.
Take the seat post and saddle off.


Yes, you read that correctly.

Stand over your seatless bike, and clip in on one side.
Bring that clipped in foot up so your crank arms are parallel to the ground.
With both hands on the handlebars, and brakes in reach, now push that pedal down.

Your bike will have no choice but to go forward, and you will have no choice but to raise your other foot off the ground, so all your weight is on the clipped in peddal.

Then coast there, with your clipped in foot down and your other foot free momentarilly.

Don't worry about clipping the other foot in yet.

Now brake and put your unclipped in foot back down on the ground.

Repeat a zillion times.

Getting started isn't about continuing to pedal. It's about pedalling ONCE hard enough to be able to coast for a few seconds.

When you can do that a few times in a row, just push, coast, stop. Push, coast, stop, then put your seat post and saddle back on, and put it on at the proper height.

Don't worry about sitting on it. You won't be sitting yet.

Just do the same exersize again, without worrying about sitting on the saddle.

Push, coast, stop. Push, coast, stop.

Now you can add in the last step:

Push, coast, sit down, stop whenever you want.