iPad Pro will not turn off while charging

Thanks for the tip. I just received an iPad Pro 11" today, and had the same problem. I was using an existing charger and a cable from my cable collection. I swapped out the charger and cable that came in the iPad box and it now stays off while charging.

An iPad will automatically restart when connected to its Power Adapter. That said, you should be able to shut-down the iPad while charging - should you choose to do so. This behaviour is unchanged with iPadOS 17.x.

If your iPad persistently restarts during charging, this might suggest a problem with your Power Adapter or the charging cable - noting that both the Power Adapter and USB-C cables incorporate active electronic components.

Charge and monitor the iPad battery - Apple Support

Troubleshooting generally requires substitution of the Power Adapter and cable for another known-good item. Most models of iPad require a Power Adapter rated at 12W (i.e., 2.4A @5V) or greater to reliably charge. 5W Power Adapters (1.0A @5V) intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow. Recent models of iPad are supplied with a 20W USB-C Power Adapter.

Some third-party USB-C power adapters (and portable PowerBanks) may not support USB PD (Power Delivery). Power Delivery mutually negotiates the charging voltage; the source, load and cable are all elements involved in the negotiation protocol. Unless the Power Adapter explicitly supports USB PD, it will almost certainly fail to charge the iPad; proprietary charging standards, such as QC (Quick Charge), are not supported.