[Android Central Question]

So today I was on my phone and suddenly it decided to restart and whenever I tried turning it on it would freeze on the starting screen and restart again. I decided to take the back casing of the phone off and it worked for a while. Then later on whenever I scrolled through an app it froze and glitched out before restarting, at one point the starting screen was also glitched out. I've tried taking the battery off and putting it back on again which tends to start up the phone before crashing again.
Also it keeps saying that the SIM card has been removed and requires a restart but yet it's in it's place (don't know if that might be related)
Does anyone have any idea what's going on with my phone? It started when I was updating some apps on google play i.e snapchat, youtube etc