Restarted my desktop PC after 3 weeks vacation. After all the updates were completed (Windows 10 and FireFox 118.0.1 among several others) I opened FireFox to access bbc.com and YouTube. During 90 minutes there were 7 or 8 crashes. Tried Chrome and after 2 further crashes started investigation.
Error messages suggested out-of-memory errors. Task manager and Resource monitor showed that "Commit Charge" was at 100%. Using MS Settings I checked Background apps and found that many MS applets were now active. I cleared all non-essential MS background apps and reduced "Commit Charge" to 12%.
Since then there have been no further Firefox or Chrome crashes.