Starter Motor problem

I have a 1987 2.5 normally aspirated Diesel that has been starting without any problems however today when i was out and about I turned the key and there was no action from the starter motor , I turned the key many times and there was no response from the starter motor , got a tow start and headed home . With the car parked up I switched off the engine and tryed to restart , the engine turned over straight away , i repeated this many times every time it started , any ideas what the problem is ?

Check the small wire on your starter motor for a bad conection - or it could be a dodgey IGN switch .
Bets are on the starter motor wire tho atm .

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Found a rather dodgy connection on the wire you suggested, nipped it up now hoping for the best , thanks for your reply