In Options -> Multiplayer -> Advanced there's an option called "Suicide after choosing a player class". What does it do? Is it a good idea to check/uncheck?
If you choose to change your role, if you have 'Suicide after choosing player class' enabled, you will die immediately and start to respawn as your new role. If disabled, the class change won't take place until you die in battle (or the round ends).
Note: this death will be counted as a Suicide, you if you are one to worry about your kill/death ratio, I'd disable it.