Engine clicks but wont turn over

Battery cables ! Do you know what voltage drop testing is ? Starter Voltage Drop

Is there any sound, like a click, the starter spinning?
This will indicate the battery is bad or a loose connection on the battery.

Does the engine turn over, or is it just silent?
If the engine turns over, the problem could be no spark or bad "Main Relay"
Hope this helps.

Dead Battery?

Have you ever chagned your timing belt?

do the basics. spark test, fuel pressure and injector signal. i got my money on the fuel pump

Make sure your battery terminals are clean, also, have the battery checked as well.

tap the solenoid on the starter probably a bad starter solenoid.

Sounds the starter is no good (sometimes they'll work intermittently for a while before they totally **** out). Of course it could just be a starter wiring problem (sending wire).

I would have the battery tested. When they get cold they get weak. Next I would look at the wires on the starter to see if their loose.

You might have to change the spark plugs or at least have them cleaned.