Car sometimes won't start randomly?

I have a ford ka, that randomly doesn't start there isn't any pattern with it. When it starts is perfectly fine, its 11years old.

It sometimes sounds like its going to start but then doesn't, always fire. I cycle the key a few times and it will eventually go. If I start it every few hours its fine, bit if I leave it it doesn't want to start.

Its had the spark plugs changed and some other sensors as well as the leads to the engine (I'm not sure the correct names) the car it self sounds better but it still sometimes doesn't want to start.

Any ideas why or is it just getting to the end of its life?

I would go get it looked at

I don't think that means it is ready for the junkyard, but that may depending on the overall condition, if there's a lot of rust, engine smoking, muffler system totally gone, etc, then the costs / benefit may not make sense.
If not then it would be ok, or you may want to sell it and get a newer car if you can afford it.
Repair - a professional mechanic should be able to identify the problem. You may have to leave the car there a few days so they can cold start it.
Possible problems,
Bad ignition switch
fuel pump.
fuel filter clogged,
coil pack,
crankshaft position sensor

Replace the battery

Sounds like a fuel pressure problem… You might have a leaky injector which is draining down pressure over time or bad check valve in tank unit, clogged fuel filter, weak fuel pump, etc.

The way the fuel system works is that when you turn the ignition key to On position just before starting, the computer runs the fuel pump via the pump relay for a few seconds to pressurize the fuel system for proper starting… Then it turns the pump off until it sees an rpm signal from the crank sensor that the engine is running and turns the pump back on via the pump relay. A pressure regulator on the engine fuel rail also maintains proper pressure and sends any residual fuel /excess pressure back to the fuel tank.

So if one of the injectors has a dirty/clogged tip and dribbles out fuel while sitting, it can cause weak fuel pressure at starting… The fuel pump needs more time to repressurize the system… Causing a hard starting condition… But may run fine otherwise. Injectors can get dirty and clog the tips over time. A leaky injector may result in some black smoke from the exhaust after starting from the excess fuel getting into a cylinder.

You can try running some Seafoam or Techron fuel additive in the gas tank per label directions… Or use a double size dosage for a tank or two, which might clean the injectors… That may help starting. Or as a temporary measure, turn the key to On position but do not start right away… Let it sit for a few seconds and then try starting to give the fuel pump time to repressurize the system.

You may need to have a shop test for proper fuel pressure and /or see if pressure bleeds down over time which might indicate other problems like a leaky injector, etc… Or have the injectors removed and professionally cleaned/tested for proper spray patterns. Given the age of the car, it 's likely due for some basic cleaning of items like injectors, clean the IAC valve which can get crudded up with soot and affects proper starting/idle speeds, clean the MAF sensor, clean throttle body, etc. And change fuel filter if due.

Replace the cap and rotor, very common on old fords.