This has happened for me - and I believe I found out it was because the camera indexes the entire memory card while booting up - and the more packed the memory card was, the longer it took at boot.
I would begin troubleshooting your device by archiving the data from the card, reformatting the card and restarting with an empty, newly-reformatted card.
All I know is I was just about to go out and buy a new Flash Gun for my 5D MkIII as both my flashes had failed, the problem I realised was I hadn't used my Flashes for a couple of years, they were not well used but both my 580EX ii and my 430EX failed to even show a glimmer of a spark. Then I read about cleaning the contacts with a slightly damp cloth ...
It really sounds like you've gotten hold of some 12 exposure film rolls. Loaded carefully without using any more leader than absolutely necessary, one can get an extra shot out of them. It's the same thing with 24 and 36 exposure rolls. One can usually get 25 and 37 frames, respectively, with most 135 format cameras. Self-winding cameras that first appeared ...
Have you taken the battery out for 24 hours, and then rebooted the camera?
On the D70, I am not sure that a factory reset does anything other than change settings, so that may not help.
Sounds like the display hardware. If so, the service depot is your only practical option.