iphone5 bugs

After several years my iphone5 suddenly bugs several times a day. 2 different bugs:

#1 the screen jams with lines appearing all across, display turns red and black, dims and then the device reboots by itself and goes back to totally normal. This happened three times in the past week.

#2 apps won't launch or will quit for no reason. this requires a reboot and everything goes back to normal. started after installing ios 9.3.4 and no change since i installed 9.3.5.

I did several reboots, restored the phone as a new phone twice already. any suggestions? thanks!!

Hervé