W211 Intermittent Starting Problem....Help!

[240diowa]

I have a 2005 E320 (gas) with a intermittent starting problem:

- Sometimes when I turn the key the starter does not engage (no clicking etc). no sounds

- Sometimes the starter makes a "clunk sound' like it is trying to engage but not enough power.

- Other times if you keep the key in the start position for several seconds it will start. Seems to be worse the lower the temperature.

My thought was I have a bad solenoid on the starter so i replaced the starter but still have the same issue. I have also replaced the starter relay.

Alternator output is 14.8 volts. Battery was tested and is good. Have cleaned the battery terminals and the also the main power feed junction under the passenger side floor mat (saw no corrosion etc).

No codes or warning lights

Was thinking maybe a bad ground somewhere??