Each restart of my Time Capsule, the orange light fix all the time

Sorry but I think we have a language issue.

Do you mean restart or reset??

If your TC is not reliable we need to know what model and firmware it is? How old it is?

How is it setup in the network? What modem router you have? Is it plugged in by ethernet? In bridge or router mode?

I also need to know the OS on the computer.

If you use Yosemite.. expect continuous issues until Apple patches it.

Yosemite is a big problem.

Is the LED solid or flashing??

If flashing please open the TC in the airport utility and find out why it is flashing.. if you cannot get to that point.. factory reset and start again.

Factory reset universal

Power off the TC.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the TC to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.

N.B. None of your files on the hard disk of the TC are deleted.. this simply clears out the router settings of the TC.

Make sure you have ipv6 set to link-local only in the computer.

You can also do a manual setup by ethernet..

https://discussions.apple.com/thread/5800974?tstart=0

Or use the airport utility in iOS which is now far more reliable than Yosemite.. heck even windows is more reliable than yosemite.

Airport Utility shows "unexpected error - please try again" when connecting to Time Capsule

Airport Utility shows "unexpected error - please try again" when connecting to Time Capsule

Airport Utility shows "unexpected error - please try again" when connecting to Time Capsule

Solid LED means the disk is dead.. it will have to be replaced .. Hard disk or the whole Time Capsule if it is still under warranty.

The warranty depends on where the Time Capsule was purchased. In the U.S. and Canada, it is one year. In a number of other countries, it is two years.

If you have AppleCare on one of your Macs, and the Time Capsule is less than 3 years old, it is probably covered.

Check with the Apple Store on details.

Do you think that my modem can impact the TC start up phase?

Sorry, but no.