Ipad mini 3 (model nr. A1599) running IOS 8.0 crashing often.

A Few months ago, my husband and I bought this iPad and since a few weeks it started to crash more and more. When I was using it today it did it sometimes every few minutes. It turns off and on automatically. The screen turns blue and then black till it restarts and shows the apple symbol. It returns then to lock screen. Datas seem to be saved though, it remembers tabs which where open. It happens using different apps (we use mainly safari, gmail and facebook, it is crashing on all three). . Sometimes it is just the app which crashes and the iPad simply retunrs to the Homescreen (this happene also with the Photo app). As far as I know there hasn't been any big update in the last time, a few apps have been added. Any idea what could be the cause? ANy experiences with the same issues and suggestions as to how to fix it? Thanks everybody!