It is completely normal for any pet, not just a budgie, to not react completely well to being in a new environment.
01.
This may not seem to you like the likely reason, but your budgie might even think that you like it when it bites you.
02.
Budgies can become very territorial. If it thinks that you are trying to take stuff out of its space, it may become defensive.
03.
This is due to changes in their hormones, which will cause your budgie to become aggressive.
04.
If your budgie is bored, it may bite you so that it can try to get your attention. Your budgie is trying to tell you that you aren’t satisfying its needs.
05.