why my pages links are always time out?

Dear All,

I have a problem for my website

1. all of my website pages are working. but I use some broken link checkers and they shows that most of pages are timeout.

I check those timeout link one by one, they can open

who can figure out what is the problem?

for example: status link

1 time out xxxxx

1 time out xxxxx.com/xxx

1 time out xxxxx.com/xxx

500 internal sever xxxxxx.com/xxxx

something like that

P.S: it is using apache running

2. please kindly inform me how to fix it the problem.

waiting for early reply

Thanks