IOS 15.4 software update

No, I don't have this issue, running iOS 15.4 since March 14th.

Which iOS version is installed on your iPhone at the moment?

To update, iPhone:

• Connect to wall power with the adapter (not using Low Power Mode)
• Connect to the Internet using Wi-Fi (not using Personal Hotspot or VPN)
• Have enough free space (<> 6 GB)
• Not running iOS Beta (if yes, delete the Beta Profile)

See if this helps: Updating iOS: common issues and solutions - Apple Community

Try a => Force restart iPhone - Apple Support

Also check if you already have a version downloaded:

Settings > General > iPhone Storage > go through the list here and delete if found.

iPhone storage.

FYI: iCloud storage do not increase what you have on iPhone

iCloud is use for backups and syncing.