first check the cable connections from battery, if u just bought it there could be a disconnection from the cables. if not 99% starter motor failure. if you go to service they will charge you around ~3000 QR for starter motor + 500 QR or more for labour. I dont know where is the starter motor excatly in trailblazer but some cars, it is very hard to reach it and if trailblazer is one of those, your labour costs could reach around 1000 QR or more. My advice is call a break down car service and tell them to take your car to industrial area, street 19 al-biroj garage. Number should bi 34 or 36 i can not remember. the mechnics are very good there. they can fix it for a very cheap price. send my greetings to Mr. Talal, my name is jan, if he can not recognize tell him red 350Z he will recognize and will give you extra discount :)