Syrian Hamster Stopped Running On Wheel, Chews On Cage

[michiiyee]

Hello!
I recently got a hamster a few months ago and recently upgraded her to a prevue hamster cage and silent runner wheel. She absolutely loved her wheel but about a week ago she stopped using it as much. She will run for a little after waking up but then will climb to the top corner of her cage and bite at the bars non-stop. I've checked to make sure the wheel still works and everything seems fine. Whenever she does this I try to put her back over by the wheel but she just goes right back to chewing the bars. Is there anything I can do to stop this? I know it's a sign of stress I'm just not sure what she is stressed from. I've been looking into getting more toys for her but not sure what some good ones are. If anyone has suggestions for anything please let me know!