Shaking Car

I have a 2001 Mitsubishi Eclipse, It will shake vigorously when it is in gear with my foot on the brake,(say at a stop light). But as soon as i let off of the brake and press on the gas the shaking completely stops. But as soon as I stop again it starts to shake again. any ideas?

Auto or manual transmission?

Are you having any problems with the cabin heater?

How many miles are on it? How well have you kept up to date on maintenance? And I don’t mean oil changes. How old are the spark plugs and wires? Fuel and air filters? Its likely that your engine is just not running quite right.

Have the vacuum lines to the brake master cylinder checked, if applicable.

Its an automatic transmission, and yes I am having a little trouble with the heater. It doesn’t get very hot especially when idle.

just over 130,000 miles. I’ve been pretty good with the maintenance, although I have never changed the spark plug wires. The air filter is in good shape, but im unsure about the fuel filter.