HELP! 2001 Mercury Marquis problem

Can anyone help! When I started my car today (2001 Mercury Marquis) it seemed as if it was cold..I just thought it had sat for 2 days so that was the problem BUT as I drove it it shook..Then after driving about 10 minutes the check engine light came on. I started driving home & noticed if I went 45 miles per hour or faster the check engine light started blinking..so I drove home at 40 miles an hour with it driving rough. Can anyone out there tell me what they think it is??? PLEASE?

Just to let you know...We found the problem! And it wasn't the transmission..whew!! We needed new sparkplugs....just letting you all know in case you have the same problem!! New sparkplugs...a good tuneup and it is going fine!