Hi,

a time delay is quite hard to implement - and you'd also need something like a beeper telling you the timer started - otherwise you'd be facing the same trouble just a few seconds later.
Voltage spikes due to interferences are no problem - a mechanical contact will not act at all as the energy is much to low (and even if - it would fall back immediately) and a solid state relay will just switch on for one cycle and then stop again.

If you really worry about it put a switch into the control or power line as suggested before. However in case of a spindle with VFD: never put a switch between VFD and spindle - you'll kill the VFD if you accidentially switch while running.

Christian