Recently, I have been experiencing shaking at low speeds and my check engine light has been blinking. I know they say this is normal right after a cold start, but this cannot be normal. I'm sure some of you have experienced this problem, and hopefully you might have some good suggestions for me. Thanks.

You should go to autozone and have your codes scanned. I still think they do it.
Or bring it to a dealer and have the codes scanned.

Is the shaking because the truck is having a hard time keeping idle or is it shaking at regular idle RPM?

It is shaking at regular RPMs.

Take your truck and get the codes read. The shaking may be related to the problem.