When does weigela start to leaf out?
You should already be seeing signs of leaf growth, but if it has been a little colder than usual then it may take a little longer. Break the tip of one of the branches, just a few inches from the tip. If it is brittle, then keep cutting until you reach living tissue. Removing any dead growth will usually give it a kickstart.
This article will give you more information on the care of these: https://www.gardeningknowhow.com/ornamental/shrubs/weigela/growing-weigela.htm