Can I be anxious even if there's no specific reason behind it?

If there is something that you need to take care of that is stressful this is a legitimate reason to feel anxious,

Yes, for sure. Sometimes, anxiety can just come and go even if there isn't a specific reason for it.

I have dealt with anxiety for most of my life. I have learned that there are many causes such as stress, trauma, genetics, or drug/alcohol use. I do not believe we are anxious for no specific reason unless it's a chemical imbalance. If that is not the case, we may feel anxiety caused by a trigger or event we aren't even aware of it. You may be able to pinpoint the reason and/or you can just try to better manage it. I have found that combating anxiety helps. I take walks, do breathing exercises, journal, get enough sleep, eat healthily, drink plenty of water, and avoid caffeine. Remember to take death breaths and and practice self-care.