I have to agree with Jeff. If you do not have permissions to restart the agent, have your SA do it. If you need those permissions, put in the request and case for it. Finding a way around a security lock down is exactly why I feel DBA's aren't as trusted as they should be. If there's a declared split in responsibilities, don't work around it. If they get tired of you calling every day for menial tasks that you could do with a bit more permissions, they'll fix your permissions. If not, when that server is down at 2 am and you can't fix it, you can always site back to where you asked for permissions and it was denied.

I wouldn't risk my job over stepping when you can fix the greater issue or just have one less thing to worry about.

As A side note, I've had Sys Admin level access on all but 3 servers I've worked on. It definitely makes the job easier... but that's all. Just easier. The work still gets done and everything still gets fixed, it just requires an additional person on the call.