Shaking while in drive

[00tothemax]

Yesterday on a completely cold start I put my car into drive and it was shaking non stop, as if someone was trying to push my car from the back while I had my foot on the break. I threw it back in park, no shake. Then I drove a bit and the service engine light started blinking at a constant interval, and wouldn't stop. I pulled over, turned the engine off and waited about two minutes. After turning the engine back on, everything seemed fine. What could be the problem?

[dr-rjp]

If you can reproduce the shaking, keep ypur eye on the RPM's when it happens and let me know what readings you got.