Sluggish performance after updating to iOS 18.0

I'm noticing this in lots of different apps - the screen keeps freezing when I interact with anything (e.g. inputting text or clicking things). If I wait, eventually it unfreezes and whatever I'd been trying to do happens, but it's happening so often - and the wait is so long (usually at least a minute) - that the iPhone is almost unusable for anything that involves typing or clicking. I have an iPhone SE (3rd generation) and it was fine before the update, and I haven't changed anything else since. Is this just me, or are others seeing this sort of thing? That's the first thing I need to know, before trying to work out what to do about it!