Crash and reboot like it has a heat problem

I was wondering if anyone have a solution to an iPAD 3 crash / reboot problem.

Best way of describing this is the iPAD3 crashes after a while (30-60 min) using it, somewhat similar to a PC having heat problems or a memory leak.

When the IPAD3 comes back on, it keeps crashing within 2-5 min going forward.

After a cool period (typically 24hours) it can run for 30-60min again and then the problem reoccurs.

Many hard reset and restores later Im about to give up. IOS version is 9.2 and the problem started around 8.4.1. Any idea on what could be wrong? and a solution?

brgds Mikkel