Better get the computer check done at swaidan guys, it cost only 75 aed to see what fault code its showing rather than blowing money in guesses. These electrical problem may become very sticky at times.
Practically and theoretically speaking YOU JUST CANT CHECK 100% unless its installed in the car.
So go for trust worthy seller or buy with some 15 days guarantee at least.
However you can open the gear with mechanic and let him diagnose it visually that nothing is chipped or broken inside. This covers only 40% - 50% risk. Rest still on luck. So good luck dude.
It must be hot plugs, and it seems pretty normal.
If you have any other issue like car overheating on highway, traffic. Or rough idling, consuming more fuel, starting problem, smoke comes out, missing happening then you can change the plugs.
hello i am the owner of a peugeot 406 2000 and a very strange problem just occurred that is the speedometer had stopped working altogether.can i fix it by my self or it needs to be done professionally