OM, MM Trouble

Hi all, I have recently just learned how to fly the PIC and everything is going great in my flight, I turn for the final apporach (the LNAV and VNAV) are off with the LOC or APP on, then when I hit the MM or the OM the plane suddenly banks severly up or down. This has happened to me while on the ILS at YYZ and KCH. Most of the time I managed to recover but it is annoying.I am not using a joystick, so I have no clue as to what is causing this.Any comments or suggestions would be great.Thanks in advance,Mike L