Is it safer to use tor bridges or normal access points in order to hide the IP?
I noticed that when I use bridges, Google asks me almost always to prove that I am human and not a pc. When I don't use bridges it happens fewer times.
It doesn't matter whether you use a bridge or not. You're experiencing a coincidence, not some actual relation between using bridges or not.
Your ISP should not be able to tell what websites you are visiting with Tor unless they can decrypt the packets. They would have to peel away each layer of the onion, if you will. My ISP is also hostile to proxy services like Tor. I'm still trying to find away around it. I can connect to Tor, with or without a bridge, but then it locks up. My ISP starts blocking the packets so I can't go anywhere. They appear to be running some kind of packet inspection. I have had success with a vpn service that used antiDPI or SSL VPN, but not an open vpn, though that still doesn't help me use Tor since it uses its own vpn. I'm still trying. Hopefully I'll find a way soon. It's possible that your ISP has gathered a list of Tor bridges on their own, posing as individuals, in order to create a list of bridges to block.
Therefore, Tor bridge relays are not necessarily safer to use
This is wrong.
There is a benefit and a good reason to use bridges even if you can connect to the network normally. Bridges add an extra layer of anonymity since they look like normal traffic and don't reveal the fact that you are connecting to the tor network. Therefore this makes it safer to use a bridge. This can be researched at https://torproject.org.
It doesn't matter whether you use a bridge or not. You're experiencing a coincidence, not some actual relation between using bridges or not
This however is more likely than not to be true.
It is my understanding (which may be limited) that Tor connections can be filtered (blocked) by your ISP since there is a publicly available list of relays. This would have to be an ISP that filters all connections to the internet (think China).
Since there is not a publicly available list of all bridge relays, you will have have a much better chance of not being blocked while using them.
Even if an ISP can tell that you are running Tor, that does not mean that they can tell what sites you are visiting or what exactly you are doing. Therefore, Tor bridge relays are not necessarily safer to use and you do not need to use them if your are already able to successfully connect to the Tor network without them.
It is safer to use bridges. I am using bridges most of the time, when I use #Orbot. However there's no need for you to use them, if your #ISP doesn't block your connection to #Tor.