Got phone repaired, now the vibration feels weird

"Got phone repaired ..."

Was the repair done at an Apple Store or Authorized Apple Service Provider?

• Yes. Return there, explain your issue, and seek assistance.
• No. You had an unauthorized repair done on your iPhone. Apple will no longer be able to assist with this device.

You can try changing it:

How to put your iPhone on vibrate, ring, or silent mode - Apple Support

Regards

Giulio

Who repaired the phone, and what did they repair it for? In other words, what did they repair?

As sberman said, make an appointment and bring it back to Apple.