Why are all the apps giggling at the same time on my iphoneSE3

What it may mean is that you need to be more careful about not accidentally touching, and holding down on, the screen. That's what triggers the phone to go into the mode for moving or deleting app icons.

P.S. – Sometimes, if you accidentally remove an app icon from one of your screens, the app is still on the phone, and you can restore the icon on the screen with the help of the App Library. ("Move an app from App Library to the Home Screen")

Find your apps in App Library on iPhone - Apple Support

Are you in the habit of carrying the phone in a pocket with the screen against your body? The touch screen is sensitive through thin cloth. If you carry the phone in your pocket make sure you lock the screen before putting it away, and put it with the back of the phone against your body rather than the screen.

Hello ~ If the Apps are jiggling this will normally be the result of an App or any blank area on the Home Screen being touch and held down.

~Katana-San~

Hello again ~ It’s not a glitch. If you press down on a blank area of your screen it will shake or giggle. If you touch it again they will stop.

~Katana-San~

Try this and see if it fixes things. It’s called a forced restart. Instructions in the link posted below.

Force restart iPhone - Apple Support

How long have you had your phone? If the jiggling isn't being prompted by you doing a touch and hold on your screen, then it might be time to get your phone checked out at the Genius bar. But I agree, the only time that usually happens is when someone touches and holds. You can reorganize the apps on your home screen and delete apps when they jiggle.

Remove apps from iPhone - Apple Support

Remove apps

Do any of the following:

• Remove an app from the Home Screen: Touch and hold the app on the Home Screen, tap Remove App, then tap Remove from Home Screen to keep it in App Library, or tap Delete App to delete it from iPhone.

So you think your apps are laughing?

That's what giggling means:

gig·gle

/ˈɡiɡ(ə)l/

verb

laugh lightly in a nervous, affected, or silly manner.

Do you mean jiggling?

If you tapped and held down on the screen, that’s how it is supposed to work. However, I think you’re saying that just a light touch - without holding down on the screen makes the apps jiggle.