Random crashes during gameplay
Are you shutting down all non-essential programs (especially anti-virus) before starting the game? Firewalls can cause conflicts (generally on startup or loading screens, though) and overlays from graphics tweaking/monitoring programs or chat programs can also cause issues.
In the launcher settings, try switching to DirectX 11, rather than Vulkan, and see if that makes a difference.
Try lowering the graphics settings and resolution, and switch to Windowed or Fake Fullscreen display mode, to see if that will make a difference. If the monitor refresh rate is higher than 60, try setting an FPS cap in the game options for 60.
Try exiting out of the Steam client, if applicable, and starting the game directly from the '..\SteamApps\common\Baldurs Gate 3\bin' folder, by right clicking the executable (bg3.exe for Vulkan, or bg3_dx11.exe) and running as administrator.
Try right clicking the executable, select Properties, switch to the Compatibility tab and check off the 'Override high DPI scaling behavior' option (set it to Application), maybe run as administrator and disable fullscreen optimization, and set a Win 7 or 8 compatibility mode. In Windows 7, check off the option to 'Disable display scaling on high DPI settings', disable desktop composition and run as administrator.
Try verifying local files: in the Steam library, right click on the game and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Files...' button.
With the GOG version, in the (optional) Galaxy client, select the game, then the settings icon at the top right (beside the Play button) and under Manage Installation select 'Verify / Repair'.
If you check the Event Viewer, does that give an error code or 'Faulting Module' file name that might help identify the cause of the crash?
- click Start (or WinKey-R), then type "event viewer" into the search box. in Windows 10, 'event' should bring up 'View event logs'.
- after starting the Event Viewer, expand 'Windows Logs' in the left column and select 'Application'
- in the center column, look for a recent error for the game (maybe sort by Date and Time, or search for 'bg3')
- check the information under the 'General' tab below the list of events, starting with "Faulting application name..."
Try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.
Maybe try creating a new Windows administrator user account, switch to that account and try starting the game from there, directly from the executable. If the game doesn't crash frequently enough to make it feasible to test in a new game, you may need to copy your latest save over from your current user account.
Each save is a folder in the 'C:\Users\<UserName>\AppData\Local\Larian Studios\Baldur's Gate 3\PlayerProfiles\<ProfileName>\Savegames\Story' folder. The fastest way to get there would probably be to copy the line below into the location bar in Explorer and hit Enter, then browse down from there.
%LocalAppData%\Larian Studios\Baldur's Gate 3\PlayerProfiles
If that doesn't help, please contact support with a dxdiag report (WinKey-R, type in dxdiag and hit enter, then when it finishes loading click on the 'Save All Information...' button and save the report somewhere handy). Also check the '..\Baldurs Gate 3\bin' folder (and '...\bin\db\attachments' or “...bin\db\reports”), and if there are any CrashDump files being created, zip a few together to include.
It would also help to know if there is any pattern to when the crashes happen (in or out of combat, when using skills, etc).