RIELLO OIL BURNER - ONLY STARTS WITH KNOCK TO MOTOR !?

Hello everyone

My oil boiler (1995) has a Riello G5 burner, it would not start this morning and was on lock-out when I got up etc.

The motor does not start but there is a kind of buzzing (might be a solenoid?) anyway, before it went to lock-out again I gave the motor a sharp (but light) knock with a spanner and it started and ran no problem for 6 hours.

I have tried the same trick 3 times now - knock with spanner - and each time it gets it to start and it then runs fine.

It can't be much so has anyone any ideas PLEASE?

Do motors in Riello Burners have brushes? I was thinking that the spanner knock is making the (worn out ) brushes make contact??

All Suggestions Welcomed
Many Thanks
Grahal