iPhone 12 keep beeping when plugged in

Do you mean it is a continuous "beep beep beep..."

which may suggest a non genuine badly made cable.

or it beeps once, but every time, which is normal.

There are many unknowns in your situation, Gigidubois. I try to avoid speculation on unknown circumstances to avoid unrealistic conclusions.

I recommend service.

Service Checklist:

• iPhone service pricing.
• Check AppleCare Coverage.
• Get your iPhone ready for service.

Need more help?

• Call 1-800-APLCARE.
• Contact Support.
• iPhone Support.
• iPhone User Guide.

Click ▶︎ Check Repair Status. 🔧

Good luck! 👋🏼😉