Possible reasons:
1. Problems with the fuel system:
* Clogged fuel filter
* Faulty fuel pump
* Fuel leak
2. Problems with the ignition system:
* Faulty spark plugs
* Damaged ignition wires
* Faulty ignition module
3. Problems with the starter:
* Faulty starter
* Worn or dirty starter brushes
* Problems with wiring to the starter
4. Problems with sensors:
*Faulty crankshaft position (CKP) sensor
*Faulty camshaft position (CMP) sensor
* Faulty Engine Temperature Sensor (ECT)
5. Problems with the ECU:
* Faulty engine control unit (ECU)
* Damage to the wiring to the ECU
6. Problems with the immobilizer:
* Faulty transponder
* Faulty immobilizer unit
* Interruptions in signal transmission between the key and the immobilizer
7. Other possible reasons:
*Dead battery
* Damaged timing belts
* Faulty mass air flow (MAF) sensor
Diagnostic steps:
1. Check the battery for charge.
2. Check the operation of the starter by trying to start it directly.
3. Check for spark at the spark plugs.
4. Check the fuel system for leaks or blockages.
5. Carry out diagnostics using a trouble code scanner (OBD2).
6. Contact a qualified mechanic if you cannot determine the problem yourself.