Is it because you’re accidentally hitting the top-right toggle, or because you’re accidentally double-tapping in the note content? Or both?
For the first one, you could use a CSS snippet to hide the toggle on mobile. That would force you to have to open the command palette or select from the three-dot kebab menu when you want to change modes.
For the second one, there’s a feature request to optionally disable or customize the double-tapping function: Turn off (or customize) double tap to switch to editing view.
Early on, the team tightened the sensitivity, and even though I personally am fine with the current double-tap, I feel like a time-between-taps slider would be a good idea for accessibility, like the adjustable double-click interval on desktops. I don’t recall seeing a feature request for specifically that though.