My ipad air 2 shut down randomly and reboot.

With liquid damage, you have to decontaminate the logic board before doing anything else, otherwise there will be latent issues down the road...as you are seeing.

The liquid is inside the device, on the logic board and under the shields, even under the IC's. The real problem is the sugar & mineral deposits that can cause short circuits or the corrosion that is taking place as the liquid dries and evaporates. Leaving the power on the device accelerates the process.

Unfortunately, the iPad is a more complicated device to get into

• Inspect the logic board, especially around the connectors and look for corrosion. If there is, then
• Open your device and remove the logic board (follow this guide)
• Inspect both sides of the board. Unfortunately, most of the board is covered in shields. That's usually where the damage is occurring.
• Put your board in a container with >90% isopropyl alcohol and let it sit for a while.
• Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.
• Rinse in alcohol and repeat.
• Let it air dry for a day.
• Re-assemble and hope for the best.

You should also replace the battery if it has swollen. Resist the temptation to pop it to let the gas out. A compromised Li-ion battery is a fire hazard. If the device appears to power up but behaves erratically, then use a tool like 3uTools to flash the firmware as it may be corrupted.

A professional repair shop that does water damage repair may be able to recover your phone or the data because they have access to pro-level ultrasonic baths and specialized cleaners as well as the skills to troubleshoot your board. Many shops have a no fix/no fee policy so you don't have to spend money to find out if the phone is fixable or not.