Did anybody notice extremely slow charging a phone from the USB port we have in the central console? Or is it just mine is slow..

I have 3 MB’s with USB ports in the consoles available for charging phones. They are all slow. My 2019 E450 Cab has a charging pad which is faster than the USB port but still not as fast as in home charging.

I guessed that the USB ports on my E53 Cab are version 2.0. (Only 4 contacts, therefore NOT version 3.0 or 3.1)
The power available is 5 volts at 0.5 amps, aka 2.5 watts. It is not intelligent (negotiable).

To charge faster than 5 volts @ 0.9 amps (4.5 watts) (aka USB v3.0) your device must negotiate with the charger for voltage and current.
A quick count came up with 15 different fast charge "Standards" that are somewhat interoperable.
So far as I know, fast charge happens when the device is plugged in to a fast charger, data transfer (and slow charge) happens when plugged into the car (or computer).

So what do you buy to plug in to your car's cigarette lighter socket?

Camp 1 - USB-PD (power delivery) Apple / Huawei / Motorola
Apple uses a USB-C to Lightning cable.
The others typically use a USB-C to USB-C cable.

Camp 2 - QualComm Quick Charge - Most Android devices Samsung Galaxy S8 and newer.
Newer phones use a USB-C to USB-A (Charger end)
Older phones use a USB-microB to USB-A (Charger end)
Others probably will only slow charge @ 2.5 or 4.5 watts.

On Amazon you will find cigarette lighter socket chargers that;
Have 2 PD sockets
Have 1 PD socket (USB-C) and 1 QC 3.0 socket (USB-A)
Have 2 QC 3.0 sockets
Note: QC 4.0+ is supposed to support QC and PD on the same socket and will be available soon.