2020 13" MacBook Pro M1 keeps defaulting to the lock screen while I'm browsing. Anyone know why this is happening?

Hello Conor274,  

Welcome to the Apple Support Communities.  

Start here to be sure that your Lock Screen settings are enabled as you would expect: Change Lock Screen settings on Mac - Apple Support

If you are noticing unexpected behavior, try these troubleshooting steps: If your Mac sleeps or wakes unexpectedly - Apple Support

Please contact Apple Support directly if you continue to notice any unexpected behavior: Apple Support. 

All the best! 

It may be that you have inadvertently assigned "Lock Screen" to one of the Hot Corners of your Mac. If so, then any time the cursor hits that corner the Mac will lock the screen.

Check this by going to System Preferences > Mission Control and clicking the Hot Corners button at the bottom left corner of that window.