my refurbished iPhone 7 plus randomly freezes..

I got a refurbished phone recently and ever since I updated it to iOS 11, about every week the screen will randomly freeze when i'm trying to open up an app and the only way to fix it is to manually restore the phone through iTunes on my computer.

So this is usually what happens: I try to open up an app like I normally would but it lags for a second and then the app looks like its about to open but it doesn't open. I try clicking on it again and it doesn't open the app. Then I try clicking on other apps to open them but that also doesn't work. Then I notice that the Safari app is like grayed out (it looks like when an app is updating minus the timer thing).

This issue prevents me from:

• opening up an app when the phone is unlocked
• swiping left/right
• trying to turn off my phone using the power button
• using Siri (Siri will turn on but it won't respond usually)
• calling (through Siri, responding to a call when the phone is locked/unlocked)
• texting (I can open up texts by swiping left and clicking View but i can't send texts)

Here's what I CAN do though:

• lock the phone
• open the phone with touch ID
• swipe up (control center) and down (notifications)
• receive calls (but my phone doesn't show the screen that you see when you're getting a call, it just shows the lock screen. the phone will ring but there will be no way for me to pick it up because i physically can't answer it)

This is such a big problem for me and I want to know if I'm not the only one who experiences this. It randomly froze for about the 4th or 5th time since I updated to iOS 11 and the only way I could fix this problem was by restoring my phone through iTunes (which a lot of the time is not a realistic option especially when I'm out in public and require my phone but do not have access to a laptop). When I have to restore my phone, I have to turn off Find My iPhone through icloud.com and then I have to rely on iCloud backups to save all of the information on my phone like pictures and apps. Then I have to set up my phone as if it was brand new every single time.

I'm not sure if this has to do with the fact that my phone was refurbished or if it was because I updated it to iOS 11 (but other people with not-refurbished phones who updated don't have this problem). Or maybe it's both of these things and my refurbished phone might not have the software necessary to deal with this bug for iOS 11. I updated my phone to iOS 11.0.3 in hopes that the update will fix these bugs but if it gets worse because of this update I wouldn't even be surprised.