I got a 5-speed 190E and it feels like my front brakes lock up after i drive for a while. I'm sure its the front brakes because when i start moving it feels like something is holding the car back and it struggles to move. Then after i drive for a while in that condition the engine temp. goes up to almost 120 F then a light comes on on the left side of the instrument panel that looks like this (o) [a circle inside two dashed line parenthesis]. After this light comes on the car starts driving fine. Can anyone tell me what causes this?

thats your brake pad sensor wear indicator stating that you need to change brake pads...

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

Sounds like your calipers are dragging. Old swollen brake hoses are probably the cause, as well as failing to replace the brake fluid at the specified intervals. Basically a lack of maintenance.
If you continue to drive the car like this, the pads will wear down and score the rotors(if that hasn't happened already). Worst case the fluid will heat up and boil in the calipers(since you're probably running on ten year old fluid) and blow the seals out, meaning you will lose the brakes. You may retain the rear brakes but at that point you will be in big trouble. 85% of the stopping is done by the fronts. You will then overwork the rears and they too will fail. At this point you will no longer have brakes.
I'd take the bus until I got this fixed. You can be sued big time if you get into an accident. Worse, you could kill somebody. Don't screw around with the brakes, get it fixed NOW.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Just to confirm it you can check the temperature of the brakes on each wheel after you drive. If one is sticking then it will be very hot. You can use an IR thermometer or some other kind. Be careful using your finger, you could get burned!

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

As mentioned, it sounds like the caliper pistons are sticking ... either due to rust inside the caliper cylinders causing the pistons to stick, or collapsed brake lines that prevent the caliper pistons from retracting easily. For safety sake get your brake problem evaluated and repaired immediately. The condition will only get progressively worse, and is a definite safetry hazard.

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Fred Hoelzle