When I am driving normally, when I stop and switch the engine off it sometimes wont start again.

If this is a fly by wire throttle, pedal assembly may be failing.

Sounds like the temperature sensor has gone bad. Replace it.

try cleaning the battery terminals . Good Luck

The check engine will be on if the key is on but engine not running . This is normal. If the check engine goes out when the engine starts there are no codes present . Did you check the fuel filter . Sometimes when a filter is dirty there is sedement laying in the filter canister . When the pump starts working the flow picks up the sedement and plugs any remaining open screen and stops the fuel completely . The engine stops . When the flow stops the sedement falls back allowing flow again. and the engine will run for another while . If the filter is old it should be changed anyway . Also when the engine stops check to see if there is spark at the spark plugs while cranking the engine .

Maybe the wires are grounding check for wires chaffing

I had this problem last year, it did it to me several times...It turned out to be the ignition switch. It needs to be replaced.

maybe low on coolant, check water to coolant ratio.

Low coolant,or water pump going bad.

Where exactly does it sound like it's comeing from?
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HI
THERE IS PROBLEM IN THE ANTE THEFT SYSTEM THAT CAUSE THE ENGINE WONT TO START AGAIN WHEN YOU LOCK AND OPEN IT YOU WELL RESET THE FAULT
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