There could be any number of reasons why an MCU freezes:

1) Noisy or unstable power supply
2) Inadequate power supply decoupling
3) Over or under voltage on any I/O pin that triggers CMOS latchup
4) Faulty system clock
5) Faulty RESET or brown-out detection
6) Bad programming
7) Unstable hardware
8) Extremely harsh electrical environment

Judging from your code, you are using servo motors. This puts the application in category (8).

I am experiencing the same problem at first i thought its my code so i tried blink led code attached to pin 13 it blinks after some few minutes it then stuck on or off till i press reset button on arduino board it blinks again n freezes over n over again

Moderator edit: New thread created from this.

 

Welcome to AAC.

Did you read @MrChips excellent description of possible problems?

 

I am experiencing the same problem at first i thought its my code so i tried blink led code attached to pin 13 it blinks after some few minutes it then stuck on or off till i press reset button on arduino board it blinks again n freezes over n over again

Moderator edit: New thread created from this.

Hi,

It is entirely possible your Arduino has a heating up problem or some other problem. The board itself could be just plain bad. You do have to test for this though to be sure. You would have to have another Arduino board and run that for some time and see if it halts. If it too halts, then it is something external in your setup. If it does not halt, then it is something in the board or the connections to the board.
I think this is the best way to proceed because you can isolate the problem to being either internal or external right away. Unfortunately, that takes having or buying another Arduino board, preferrable from a different seller.

The thing is, not doing this means it could take a long time to figure out what is wrong. If it is the Arduino board you could be playing with it for weeks and not knowing it's just bad.

There are noise sources that can screw up the code flow, such as a room fan turning on or turning off. This is more common when using interrupt on change pins but I guess you never know.

If you are just running the Arduino board off of a PC computer USB port, it should run ok. If not then maybe the cord is too long or the connection is bad, so try another USB cable. If possible, try another PC computer.

Narrow down the problem as much as possible any way you can as that will lead you to the problem faster.