Here are some possible pronunciations:
* VIG-der: With a strong emphasis on the first syllable and a short, sharp "er" sound at the end.
* VIH-ger: With a softer, more vowel-like "i" sound and a "ger" ending that might rhyme with "fur".
* VIG-dər: With a slightly longer "er" sound, possibly rhyming with "stir".
The best way to know how to pronounce it is to ask the person who has the surname. If you're encountering it in writing, context clues might help you guess.
For example, if you see it in a list of names from a certain region, you could try to find other names from that region and see how they are pronounced.