Depressed mood, severe fatigue, dizziness and mild nausea. can it be xanax (alprazolam) withdrawal from 0.5mg?

Possibly: If you were taking xanax (alprazolam) regularly for long enough, you can have withdrawal symptoms from it.

Xanax (alprazolam) withdrawal: Withdrawal symptoms vary & may include aches & pains, blurred vision, agitation, depression, dry mouth, dizziness, electric shock sensations, flu-like symptoms, headaches, increased sensitivity to sound & touch, insomnia, impaired concentration & memory, muscle cramps, nausea & vomiting, tremors, sweating, blood pressure changes, confusion if severe.

Unclear: If you were taking this dose only once a day, regularly, then it is unlikely to be the cause of those symptoms. But if it was more than once a day, or, if you were also taking certain other substances or medicines regularly, and you also stopped them, then the Xanax (alprazolam) could be a factor.