system restarts for every 2hours of use

Random restarting is generally attributed to overheating. Get yourself a cooling pad, or allow the system to sit somewhere it can breathe without anything getting in the way of the fans/exhaust ports.

If upon examination, you determine there is dust or other buildup in the fan, vents, or exhaust ports, You might try to vacuum them out--but do not use a metal vacuum tip (due to static electricity discharge concerns) and use some sort of mesh over the vacuum attachment opening so you don't suck up any loose small parts that have been or become dislodged.

You can try using canned air--and most people do, to try and blow out the machine without opening it up--but a word of caution. When you apply strong bursts of air directly to the fan assembly, you can easily damage the ball bearings which can cause the fan to become noisy or potentially even slow to the point of ineffectiveness.