My BLU phone was rebooting all the time.
I noticed the battery was moving around in the back of the phone.
I am a swimmer and I use silicone ear plugs to keep the water out of my ears.
You can buy these at any pharmacy.
https://www.cvs.com/shop/cvs-health-ultra-soft-silicone-earplugs-antimicrobial-protection-prodid-457795?skuId=457795
I stuck one of these ear plugs between the battery and my case.
And the battery stopped moving around inside the phone case.
And that solved the problem.
Uncle G