Can anyone help me identify the source? The rattle is getting worse and worse and I've tried holding on to the plastic part on the steering wheel, the left trim where the buttons are located, and the center trim where 4 vent is located to no avail. The sounds seems to come from the inside of the dash or near the screen. I tried putting the microfiber towel inside the steering just below the screen and inside the steering mechanism to no avail.

If yours is new, dealer should look into it for you. They’ll likely remove all the relevant trim pieces. Rattle sounds could mean bolts not tightened in the steering shaft / column ?

It's 2018, I bought it as CPO certified vehicle. But the factory warranty is still active until 2022 and this car rattles so damn much that I sent it back to the dealers like 3 times and each time new rattles appears. I tried holding on to every pieces of trim/vent/ components that I could see to no avail...

With same dealer ? If yes, I suggest to try another dealer, if possible.

I have rattling on my roof and took literally over 1 yr and 4 dealer visits to fix.

I suggest you are to ask for the shop foreman to go for test drive with you, if possible.