Remove C139. You should not have a capacitor between gate and drain.
When you press the button, C136 and C139 form a capacitive voltage divider that will switch on the MOSFET for a while.
If you want a capacitor on the output, the negative side should be connected to ground.
I often have a capacitor between gate and drain. Especially for a power distribution switch it prevents from fast switch ON of the load.
In combiniation with the drive resistance it generates an about constant dV/dt...which causes a calculable inrush current on load capacitance.
The cap also causes slow turn off. As the FET has initially zero Vds, the cap further causes the observed output pulse after switch closure because Vds can only ramp up slowly.