When the bike was running earlier I saw that the speedometer is moving even though the bike is not moving. sometimes the dashboard does not come on but the bike can be started. Guzzi was involved in small fender bender in May nothing serious and then it sat until now.
From this symptom I suspect there is a loose connection somewhere making the dash or ECU think it's getting speed pulses e.g. a loose positive or ground. Another thing I would suspect is the ignition switch, try flicking it numerous times, perhaps with the main fuses out, this might be enough to clean the contacts a bit to get a better contact. If it does improve then pull the switch apart and clean.
Check grounds around the ECU and dash. It could also be a dirty kill switch and perhaps the side-stand switch.
If you have a multimeter check the voltage at the top 2 fuses on the diagram, it should be steady 0 with switch off + 12 with the switch closed.
Needless to say disconnect the battery cables and clean the terminals, check the main ground
It's Electrickery for sure