by glow grid I am assuming you are thinking of glow plugs
without more information its quite difficult to give an accurate answer
Things to look at are-
individual glow plugs have failed, with some working and some aren't
all glow plugs have failed (due to faulty glow timer (stuck on))
all glow plugs are working (electrically) but aren't being used (faulty glow timer (stuck off))
other electrical problems causing above issues (short circuit wiring harness, open circuit wiring harness, faulty switches and/or relays)
other mechanical issues causing hard starts (low compression/worn rings/valves) or other mechanical issues that a mechanic rather than an auto sparky like me would know more about
If the engine cranks & cranks & cranks before it starts even though it's warmed up already.
crankshaft
Because the fuel pump is faulty
try the distributor module . may not be getting fire.
Crankshaft position sensor.
My car starts but it shuts off it says ck engine
If the check engine light is or has illuminated, check for codes.
You need a battery. There's a very small chance it could be something else, but from the symptoms you describe it is more than likely a bad battery.
The problem needs to be present to trouble shoot it. If guessing is your preference, the garage will provide you with good guesses. But it could get expensive. My guess is a module that would control spark.
Check for codes(possible cam sensor), check fuel pressure bleed down(possible fuel pump).
THE netural Saftey Switch could B bad .
it could possibly be a bad coil, crank shaft sensor, or cam shaft sensor.