First thing I'd suggest is trying some body surfing, so you can feel where the power is in the wave.
If you're out on the shoulder, you're not going to catch it, because there's no push, so you need to judge where the peak is and get there.
Once you've caught the wave, feel the glide and look down the line to where you're going to be next so you can judge whether you want to take a steeper path for a slower wave or angle more across the face to stop yourself nose diving.
When you have that established would be the point at which you walk up, but you can try belly boarding a few waves to give yourself the chance to think about what's happening, rather than stressing thinking "got to pop up...!"
There's a good tutorial about the Three P's of Position, Posture and Presence which may help.
Commented on New to OMBE here, hoping someone can ...
15 Sep 20:44
Welcome!
Put simply, if you imagine you have a cup of coffee in your back hand, you want to keep it up and forward so you don't spill it.
Then if you want to go up the wave, you put the cup on the lip, to turn left, you pass the coffee to the left etc.
There's a good introductory video where Clay explains the principles here:
https://train.ombe.co/programs/coffee-cup-intro-coffee-cup-stance-cardboard-surfer