Should I accept this invitation to conference PC?
If your alarm bells are ringing, but the offered position is attractive, then there are ways to check it out without causing problems.
Example: The person who's name is on this invite will have contact information outside this particular email. A phone number or email that you don't get from this email, for example, but from their institution or some such. That way, if the email is not legit you are not going through the channel it has provided. Contact that person using that independent contact info. The approach could be something like so:
Hello well-known-person-running-a-conference. I have received this email inviting me to join the PC for well-known-conference. What would be involved? How much time and effort is expected to be required? What other requirements are there?
Then if the person responds with ready information you can simply decide if the amount of work is acceptable. If they respond with "who are you and how did you get my name?" then possibly the original email is not so legit.
Is that normal, or should that ring some bells?
It is normal to have
received an e-mail inviting me to join the program committee
even better that it is for
a well-established and renowned conference
and that it
Personally, I would have already accepted the invitation.
However, I do not directly know the guy writing to me
That's normal, you can't know everyone directly. Given that the conference is well-established and renowned, you should expect to find he seems to be a respectable researcher, after I googled his name.
[T]he e-mail is not tailored at all on my profile [and] does not specify at all why they chose me
I'm not surprised, it most likely was automatically generated. Hand-crafting individual PC invitations is time-consuming and not really necessary, IMO.