Q: When IMac wakes up from sleep mode, form filling appears very slowly and as random characters and spaces. Rebooting cures until next sleep mode.

Hi ChipCarpenter,

Thanks for using the Apple Support Communities! I'm sorry to hear you are having this issue with your Mac. If you are having unusual keyboard behavior after your iMac wakes from sleep, you may find the troubleshooting steps outlined in the following article helpful (the article is aimed at slightly different but still related issues). In particular, you may want to try the SMC/NVRAM reset mentioned toward the end of the article:

If your Mac doesn't sleep or wake when expected - Apple Support

Regards