I have a weird problem; during colder weather ( 0-10°C / 32-50°F ) the central lock on the driver side and the tailgate opening button near the steering wheel don't work (both can be opened with manually with the key, thou).

After a while (10-15 minutes of driving) the central lock system opens automatically all remaining doors that did not respond in the beginning. Same goes with the tailgate button..

Any ideas how to fix it, what to check first?
Thanks!

Double check to see if the passenger side door lock switch is functional when the driver's side is inop.
What may be happening is during cold weather, the wiring harness is being pulled somewhere and disconnecting either power or ground from those switches.
Hands-on diagnosis while the fault is present will be the only way to determine what is actually going on.
Let us know!