Every time I open chromium on my raspberry pi, it just reboots sometimes even 3 or 4 times. I've read about instances of the pi crashing but my device just starts from the rainbow screen. There's also this lightning symbol on the corner of the screen, do you think it's a probable cause?
it just reboots sometimes even 3 or 4 times.
That certainly isn't because of Chrome. If it rebooted once when you opened Chrome, it might be, but it could not cause it to repeat the process unless you opened it again.
There's also this lightning symbol on the corner of the screen, do you think it's a probable cause?
That's not the cause, that's a symptom of the same problem. It indicates undervoltage, which will happen with an insufficient power supply when there is a sudden demand for current.
Opening Chrome would be a CPU intensive process drawing a lot of current.
It this is enough to cause a hard reset (i.e., the SoC shuts down because the voltage is too low, which eliminates most of the current draw, so the voltage rises again), booting is also a very CPU/energy intensive process. Your power supply likely is unable to catch up, so within a few seconds a reset is triggered again, and the process repeats until you get lucky.
You should be able to observe the red PWR LED flickering during all this as well (which is another indicator like the lightening bolt).
You need a decent 5V (or preferably, a 5.1/5.2 V) supply capable of 2.5 amps to properly power a Pi 3.
I am running a Pi 3+ with Raspian stretch as its OS, every time I ran Chromium, the Pi would crash and reboot, I started to doubt your advice about the PSU not being able to support it, especially after trying 3 different types, Samsung @ 1.7amp, Apple 1amp and a Pama 1.5Amp ? PSU , but in desperation I tried plugging it into my NAS usb port and low and behold it works perfectly, never would I have thought that there is so much diffence between 5v usb chargers (appart from current), anyway many thanks, working perfectly now! will have to look out for a decent PSU rated at 2.5A Regards Mark