Car has been sitting around for the last 2 months. Jump started it and none of the instruments are working - Rev counter, speedo, boost, fuel even the MIL light did not come on when turned to IG1 position???

Turned it off and the boost gauge and fuel gauge went up half way and stay there????

Then started it up again and the instruments worked and it seems to happen whenever it wants now???

Anyone have any ideas?Thanks again.