Immobiliser Problem of sorts ???

I have a 2002 Fiat Ducato 2000cc JTD (motorhome). The battery failed & on trying to start, the voltage went so low it reset the clock/trip mileage etc. I tried jump starting, it always starts well, but no go. I noticed, now I had a good 12volts, that the Immobiliser & Injector Fail lights were on, so no way to start.
Now, I found that after 10 mins these lights went out & all was as normal.
So fitted new battery, the 2 lights were there again so no start, waited 10 mins & they went out & all was well again........... until I switched off ..... then at the next switch on I have to wait 10 mins again & that is where I am.
Anyone any clues please ???