when trying to update my software the pop up simply spools endlessely....checking for updates. What to do?

I understand Software Update is stuck at "Checking for updates..." with no end in sight. Is that correct?

Several workarounds have been proposed, such as restarting your Mac in "Safe Mode" and checking for updates while in that mode, and / or resetting NVRAM. Try both.

How to use safe mode on your Mac - Apple Support

Reset NVRAM on your Mac - Apple Support

Related: Software Update stuck at "Checking for updates"… - Apple Community

Try rebooting the Mac and try again.

If that does not work, then boot into Safe Mode to see if you can check for updates. If this works, then it most likely means you have some third party software installed which is interfering with the normal operation of macOS. Usual culprits are anti-virus apps, cleaning/optimizer apps, and third party security software....none of which is needed on a Mac.

Sometimes you may just need to wait a day or two just in case Apple is having some issues or the Apple servers are being overwhelmed such as when a new update has just been released.