Hi,
I had same problems with my Eutikia SM 428_2003.
For rendom start look at red cable on start motor: the connection may be slack/oxidised. Anyway remove and fasten it. The contact MUST be perfect and steady.
For rendom shut down look at solenoid. Replace it or spry antoxidant inside from top. You have to remove the black rubber cover button. Than push it many times.
I hope that may help.
Buon Vento
Giovanni
EUTIKIA