I bought a Trezor Model 3 that arrived today. I was taking pictures of the "unboxing" to post in the show off your hardware wallet topic, but I noticed that when I ripped off the cover, the resin/glue wasn't very sticky. It gave the impression that the box was already opened before, then stuck it together again.
Everything besides that was normal. The hologram seal, the plastic wrap, and the security deal were normal. I'm scared to plug in to my computer.

If you took a photo when you opened the box, could you post it here, showing the glue you found wasn't very sticky? Can see it in the photo?
If everything else is fine, should you worry about this? Especially since the seal on the device is intact (unless the device itself was replaced).
I doubt you'll be able to return and replace the device under warranty, because how can you explain the reason? Because you doubt the device's authenticity?
Why are you afraid to connect it to a PC? Do you think a hardware wallet will take over your PC and steal all your crypto assets?

Well, then, boot from Live USB (Windows or Linux) and test the device with a small amount of money.
As a last resort, disassemble the device and check for any signs of tampering to remove all your doubts.